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  • R.I.P. to my old Leetcode repository, where there were 5.7k+ stars and 2.2k+ forks (ever the top 3 in the field).
  • Since free questions may be even mistakenly taken down by some companies, only solutions will be post on now.
  • There are new LeetCode questions every week. I'll keep updating for full summary and better solutions.
  • For more problem solutions, you can see my LintCode repository.
  • For more challenging problem solutions, you can also see my GoogleCodeJam, FacebookHackerCup repositories.
  • Hope you enjoy the journey of learning data structures and algorithms.
  • Notes: "πŸ”’" means your subscription of LeetCode premium membership is required for reading the question.

Algorithms

Database

Shell

Reference

Bit Manipulation

# Title Solution Time Space Difficulty Tag Note
0136 Single Number C++ Python O(n) O(1) Easy
0137 Single Number II C++ Python O(n) O(1) Medium
0190 Reverse Bits C++ Python O(1) O(1) Easy
0191 Number of 1 Bits C++ Python O(1) O(1) Easy
0201 Bitwise AND of Numbers Range C++ Python O(1) O(1) Medium
0231 Power of Two C++ Python O(1) O(1) Easy LintCode
0260 Single Number III C++ Python O(n) O(1) Medium
0268 Missing Number C++ Python O(n) O(1) Medium LintCode
0318 Maximum Product of Word Lengths C++ Python O(n) ~ O(n^2) O(n) Medium Bit Manipulation, Counting Sort, Pruning
0342 Power of Four C++ Python O(1) O(1) Easy
0371 Sum of Two Integers C++ Python O(1) O(1) Easy LintCode
0389 Find the Difference C++ Python O(n) O(1) Easy
0393 UTF-8 Validation C++ Python O(n) O(1) Medium
0401 Binary Watch C++ Python O(1) O(1) Easy
0411 Minimum Unique Word Abbreviation C++ Python O(2^n) O(n) Hard πŸ”’
0421 Maximum XOR of Two Numbers in an Array C++ Python O(n) O(n) Medium
0461 Hamming Distance C++ Python O(1) O(1) Easy
0462 Minimum Moves to Equal Array Elements II C++ Python O(n) on average O(1) Medium Quick Select
0477 Total Hamming Distance C++ Python O(n) O(1) Medium
0645 Set Mismatch C++ Python O(n) O(1) Easy
0693 Binary Number with Alternating Bits C++ Python O(1) O(1) Easy
0762 Prime Number of Set Bits in Binary Representation C++ Python O(1) O(1) Easy
0868 Binary Gap C++ Python O(1) O(1) Easy
0898 Bitwise ORs of Subarrays C++ Python O(n) O(1) Medium

Array

# Title Solution Time Space Difficulty Tag Note
0015 3 Sum C++ Python O(n^2) O(1) Medium Two Pointers
0016 3 Sum Closest C++ Python O(n^2) O(1) Medium Two Pointers
0018 4 Sum C++ Python O(n^3) O(1) Medium Two Pointers
0026 Remove Duplicates from Sorted Array C++ Python O(n) O(1) Easy Two Pointers
0027 Remove Element C++ Python O(n) O(1) Easy
0031 Next Permutation C++ Python O(n) O(1) Medium Tricky
0041 First Missing Positive C++ Python O(n) O(1) Hard Tricky
0048 Rotate Image C++ Python O(n^2) O(1) Medium
0054 Spiral Matrix C++ Python O(m * n) O(1) Medium
0059 Spiral Matrix II C++ Python O(n^2) O(1) Medium
0066 Plus One C++ Python O(n) O(1) Easy
0073 Set Matrix Zeroes C++ Python O(m * n) O(1) Medium
0080 Remove Duplicates from Sorted Array II C++ Python O(n) O(1) Medium Two Pointers
0118 Pascal's Triangle C++ Python O(n^2) O(1) Easy
0119 Pascal's Triangle II C++ Python O(n^2) O(1) Easy
0121 Best Time to Buy and Sell Stock C++ Python O(n) O(1) Easy
0128 Longest Consecutive Sequence C++ Python O(n) O(n) Hard Tricky
0157 Read N Characters Given Read4 C++ Python O(n) O(1) Easy πŸ”’
0158 Read N Characters Given Read4 II - Call multiple times C++ Python O(n) O(1) Hard πŸ”’
0163 Missing Ranges C++ Python O(n) O(1) Medium πŸ”’
0169 Majority Element C++ Python O(n) O(1) Easy Boyer–Moore Majority Vote Algorithm
0189 Rotate Array C++ Python O(n) O(1) Easy
0209 Minimum Size Subarray Sum C++ Python O(n) O(1) Medium Binary Search
0215 Kth Largest Element in an Array C++ Python O(n) ~ O(n^2) O(1) Medium EPI
0228 Summary Ranges C++ Python O(n) O(1) Medium
0229 Majority Element II C++ Python O(n) O(1) Medium
0238 Product of Array Except Self C++ Python O(n) O(1) Medium LintCode
0240 Search a 2D Matrix II C++ Python O(m + n) O(1) Medium EPI, LintCode
0243 Shortest Word Distance C++ Python O(n) O(1) Easy πŸ”’
0245 Shortest Word Distance III C++ Python O(n) O(1) Medium πŸ”’
0251 Flatten 2D Vector C++ Python O(1) O(1) Medium πŸ”’
0277 Find the Celebrity C++ Python O(n) O(1) Medium πŸ”’, EPI
0289 Game of Life C++ Python O(m * n) O(1) Medium
0293 Flip Game C++ Python O(n * (c+1)) O(1) Easy πŸ”’
0296 Best Meeting Point C++ Python O(m * n) O(m + n) Hard πŸ”’
0311 Sparse Matrix Multiplication C++ Python O(m * n * l) O(m * l) Medium πŸ”’
0334 Increasing Triplet Subsequence C++ Python O(n) O(1) Medium
0370 Range Addition C++ Python O(k + n) O(1) Medium πŸ”’
0384 Shuffle an Array C++ Python O(n) O(n) Medium EPI
0396 Rotate Function C++ Python O(n) O(1) Easy
0412 Fizz Buzz C++ Python O(n) O(1) Easy
0414 Third Maximum Number C++ Python O(n) O(1) Easy
0419 Battleships in a Board C++ Python O(m * n) O(1) Medium
0422 Valid Word Square C++ Python O(m * n) O(1) Easy πŸ”’
0442 Find All Duplicates in an Array C++ Python O(n) O(1) Medium
0448 Find All Numbers Disappeared in an Array C++ Python O(n) O(1) Easy
0531 Lonely Pixel I C++ Python O(m * n) O(m + n) Medium πŸ”’
0533 Lonely Pixel II C++ Python O(m * n) O(m * n) Medium πŸ”’
0565 Array Nesting C++ Python O(n) O(1) Medium
0566 Reshape the Matrix C++ Python O(m * n) O(m * n) Easy
0581 Shortest Unsorted Continuous Subarray C++ Python O(n) O(1) Easy
0605 Can Place Flowers C++ Python O(n) O(1) Easy
0624 Maximum Distance in Arrays C++ Python O(n) O(1) Easy πŸ”’
0643 Maximum Average Subarray I C++ Python O(n) O(1) Easy Math
0644 Maximum Average Subarray II C++ Python O(n) O(n) Hard πŸ”’ Math
0661 Image Smoother C++ Python O(m * n) O(1) Easy
0665 Non-decreasing Array C++ Python O(n) O(1) Easy
0667 Beautiful Arrangement II C++ Python O(n) O(1) Medium
0670 Maximum Swap C++ Python O(logn) O(logn) Medium
0674 Longest Continuous Increasing Subsequence C++ Python O(n) O(1) Easy
0683 K Empty Slots C++ Python O(n) O(n) Hard
0697 Degree of an Array C++ Python O(n) O(n) Easy
0713 Subarray Product Less Than K C++ Python O(n) O(1) Medium
0717 1-bit and 2-bit Characters C++ Python O(n) O(1) Easy Greedy
0723 Candy Crush C++ Python O((R * C)^2) O(1) Medium
0724 Find Pivot Index C++ Python O(n) O(1) Easy
0729 My Calendar I C++ Python O(nlogn) O(n) Medium
0731 My Calendar II C++ Python O(n^2) O(n) Medium
0732 My Calendar III C++ Python O(n^2) O(n) Hard
0747 Largest Number At Least Twice of Others C++ Python O(n) O(1) Easy
0755 Pour Water C++ Python O(v * n) O(1) Medium
0766 Toeplitz Matrix C++ Python O(m * n) O(1) Easy
0768 Max Chunks To Make Sorted II C++ Python O(nlogn) O(n) Hard
0769 Max Chunks To Make Sorted C++ Python O(n) O(1) Medium
0778 Swim in Rising Water C++ Python O(n^2) O(n^2) Hard Union Find
0792 Number of Matching Subsequences C++ Python O(n + w) O(k) Medium
0794 Valid Tic-Tac-Toe State C++ Python O(1) O(1) Medium
0795 Number of Subarrays with Bounded Maximum C++ Python O(n) O(1) Medium
0803 Bricks Falling When Hit C++ Python O(r * c) O(r * c) Hard Union Find
0807 Max Increase to Keep City Skyline C++ Python O(n^2) O(n) Medium
0821 Shortest Distance to a Character C++ Python O(n) O(1) Easy
0830 Positions of Large Groups C++ Python O(n) O(1) Easy
0832 Flipping an Image C++ Python O(n^2) O(1) Easy
0835 Image Overlap C++ Python O(n^4) O(n^2) Medium
0840 Magic Squares In Grid C++ Python O(m * n) O(1) Easy
0842 Split Array into Fibonacci Sequence C++ Python O(n^3) O(n) Medium
0845 Longest Mountain in Array C++ Python O(n) O(1) Medium
0849 Maximize Distance to Closest Person C++ Python O(n) O(1) Easy
0860 Lemonade Change C++ Python O(n) O(1) Easy
0868 Transpose Matrix C++ Python O(r * c) O(1) Easy
0885 Spiral Matrix III C++ Python O(max(m, n)^2) O(1) Medium
0888 Fair Candy Swap C++ Python O(m + n) O(m + n) Easy
0896 Monotonic Array C++ Python O(n) O(1) Easy
0905 Sort Array By Parity C++ Python O(n) O(1) Easy
0909 Snakes and Ladders C++ Python O(n^2) O(n^2) Medium
0915 Partition Array into Disjoint Intervals C++ Python O(n) O(n) Medium
0918 Maximum Sum Circular Subarray C++ Python O(n) O(1) Medium
0922 Sort Array By Parity II C++ Python O(n) O(1) Easy
0923 3Sum With Multiplicity C++ Python O(n^2) O(n) Medium
0927 Three Equal Parts C++ Python O(n) O(1) Hard
0932 Beautiful Array C++ Python O(n) O(n) Medium
0941 Valid Mountain Array C++ Python O(n) O(1) Easy
0945 Minimum Increment to Make Array Unique C++ Python O(nlogn) O(n) Medium
0947 Most Stones Removed with Same Row or Column C++ Python O(n) O(n) Medium Union Find
0949 Largest Time for Given Digits C++ Python O(1) O(1) Easy
0950 Reveal Cards In Increasing Order C++ Python O(n) O(n) Medium
0952 Largest Component Size by Common Factor C++ Python O(f * n) O(p + n) Hard Union Find
0954 Array of Doubled Pairs C++ Python O(n + klogk) O(k) Medium
0961 N-Repeated Element in Size 2N Array C++ Python O(n) O(1) Easy
0978 Longest Turbulent Subarray C++ Python O(n) O(1) Medium
0985 Sum of Even Numbers After Queries C++ Python O(n + q) O(1) Easy
0989 Add to Array-Form of Integer C++ Python O(n + logk) O(1) Easy
0997 Find the Town Judge C++ Python O(t + n) O(n) Easy
0999 Available Captures for Rook C++ Python O(1) O(1) Easy
1002 Find Common Characters C++ Python O(n * l) O(1) Easy
1007 Minimum Domino Rotations For Equal Row C++ Python O(n) O(1) Medium
1013 Pairs of Songs With Total Durations Divisible by 60 C++ Python O(n) O(1) Easy
1014 Best Sightseeing Pair C++ Python O(n) O(1) Medium
1018 Binary Prefix Divisible By 5 C++ Python O(n) O(1) Easy
1020 Partition Array Into Three Parts With Equal Sum C++ Python O(n) O(1) Easy
1030 Matrix Cells in Distance Order C++ Python O(m * n) O(1) Easy
1031 Maximum Sum of Two Non-Overlapping Subarrays C++ Python O(n) O(1) Medium
1051 Height Checker C++ Python O(nlogn) O(n) Easy
1052 Grumpy Bookstore Owner C++ Python O(n) O(1) Medium
1072 Flip Columns For Maximum Number of Equal Rows C++ Python O(m * n) O(m * n) Medium
1074 Number of Submatrices That Sum to Target C++ Python O(m^2 * n) O(n) Hard
1085 Sum of Digits in the Minimum Number C++ Python O(n * l) O(l) Easy πŸ”’
1089 Duplicate Zeros C++ Python O(n) O(1) Easy
1093 Statistics from a Large Sample C++ Python O(n) O(1) Medium
1099 Two Sum Less Than K C++ Python O(nlogn) O(1) Easy πŸ”’
1109 Corporate Flight Bookings C++ Python O(n) O(1) Medium Line Sweep
1144 Decrease Elements To Make Array Zigzag C++ Python O(n) O(1) Medium
1169 Invalid Transactions C++ Python O(nlogn) O(n) Medium Sliding Window, Line Sweep
1176 Diet Plan Performance C++ Python O(n) O(1) Easy Sliding Window
1184 Distance Between Bus Stops C++ Python O(n) O(1) Easy
1200 Minimum Absolute Difference C++ Python O(nlogn) O(n) Easy
1208 Get Equal Substrings Within Budget C++ Python O(n) O(1) Medium Sliding Window
1222 Queens That Can Attack the King C++ Python O(1) O(1) Medium
1252 Cells with Odd Values in a Matrix C++ Python O(n + m) O(n + m) Easy

String

# Title Solution Time Space Difficulty Tag Note
0005 Longest Palindromic Substring C++ Python O(n) O(n) Medium Manacher's Algorithm
0006 ZigZag Conversion C++ Python O(n) O(1) Easy
0008 String to Integer (atoi) C++ Python O(n) O(1) Easy
0014 Longest Common Prefix C++ Python O(n * k) O(1) Easy
0028 Implement strStr() C++ Python O(n + k) O(k) Easy KMP Algorithm
0038 Count and Say C++ Python O(n * 2^n) O(2^n) Easy
0043 Multiply Strings C++ Python O(m * n) O(m + n) Medium
0058 Length of Last Word C++ Python O(n) O(1) Easy
0067 Add Binary C++ Python O(n) O(1) Easy
0068 Text Justification C++ Python O(n) O(1) Hard
0125 Valid Palindrome C++ Python O(n) O(1) Easy
0151 Reverse Words in a String C++ Python O(n) O(1) Medium
0161 One Edit Distance C++ Python O(m + n) O(1) Medium πŸ”’
0165 Compare Version Numbers C++ Python O(n) O(1) Easy
0186 Reverse Words in a String II C++ Python O(n) O(1) Medium πŸ”’
0214 Shortest Palindrome C++ Python O(n) O(n) Hard KMP Algorithm Manacher's Algorithm
0242 Valid Anagram C++ Python O(n) O(1) Easy LintCode
0271 Encode and Decode Strings C++ Python O(n) O(1) Medium πŸ”’
0273 Integer to English Words C++ Python O(1) O(1) Hard
0306 Addictive Number C++ Python O(n^3) O(n) Medium
0383 Ransom Note C++ Python O(n) O(1) Easy EPI
0405 Convert a Number to Hexadecimal C++ Python O(n) O(1) Easy
0408 Valid Word Abbreviation C++ Python O(n) O(1) Easy πŸ”’
0415 Add Strings C++ Python O(n) O(1) Easy
0420 Strong Password Checker C++ Python O(n) O(1) Hard
0424 Longest Repeating Character Replacement C++ Python O(n) O(1) Medium Sliding Window
0434 Number of Segments in a String C++ Python O(n) O(1) Easy
0443 String Compression C++ Python O(n) O(1) Easy
0459 Repeated Substring Pattern C++ Python O(n) O(n) Easy KMP Algorithm
0468 Validate IP Address C++ Python O(1) O(1) Medium
0482 License Key Formatting C++ Python O(n) O(1) Easy
0520 Detect Capital C++ Python O(l) O(1) Easy
0521 Longest Uncommon Subsequence I C++ Python O(min(a, b)) O(1) Easy
0522 Longest Uncommon Subsequence II C++ Python O(l * n^2) O(1) Medium Sort
0524 Longest Word in Dictionary through Deleting C++ Python O((d * l) * logd) O(1) Medium Sort
0527 Word Abbreviation C++ Python O(n * l) ~ O(n^2 * l^2) O(n * l) Hard πŸ”’
0539 Minimum Time Difference C++ Python O(nlogn) O(n) Medium
0541 Reverse String II C++ Python O(n) O(1) Easy
0551 Student Attendance Record I C++ Python O(n) O(1) Easy
0556 Next Greater Element III C++ Python O(1) O(1) Medium
0557 Reverse Words in a String III C++ Python O(n) O(1) Easy
0564 Find the Closest Palindrome C++ Python O(l) O(l) Hard
0591 Tag Validator C++ Python O(n) O(n) Hard
0616 Add Bold Tag in String C++ Python O(n * d * l) O(n) Medium πŸ”’
0647 Palindromic Substrings C++ Python O(n) O(n) Medium Manacher's Algorithm
0648 Replace Words C++ Python O(n) O(t) Medium Trie
0657 Robot Return to Origin C++ Python O(n) O(1) Easy
0678 Valid Parenthesis String C++ Python O(n) O(1) Medium
0680 Valid Palindrome II C++ Python O(n) O(1) Easy
0681 Next Closest Time C++ Python O(1) O(1) Medium
0686 Repeated String Match C++ Python O(n + m) O(1) Easy Rabin-Karp Algorithm
0696 Count Binary Substrings C++ Python O(n) O(1) Easy
0720 Longest Word in Dictionary C++ Python O(n) O(t) Easy Trie
0722 Remove Comments C++ Python O(n) O(k) Medium
0751 IP to CIDR C++ Python O(n) O(1) Medium
0758 Bold Words in String C++ Python O(n * l) O(t) Easy πŸ”’, variant of Add Bold Tag in String
0791 Custom Sort String C++ Python O(n) O(1) Medium
0796 Rotate String C++ Python O(n) O(1) Easy KMP Algorithm Rabin-Karp Algorithm
0804 Unique Morse Code Words C++ Python O(n) O(n) Easy
0806 Number of Lines To Write String C++ Python O(n) O(1) Easy
0809 Expressive Words C++ Python O(n + s) O(l + s) Medium
0816 Ambiguous Coordinates C++ Python O(n^4) O(n) Medium
0819 Most Common Word C++ Python O(m + n) O(m + n) Easy
0820 Short Encoding of Words C++ Python O(n) O(t) Medium Trie
0824 Goat Latin C++ Python O(n + w^2) O(l) Easy
0831 Masking Personal Information C++ Python O(1) O(1) Medium
0833 Find And Replace in String C++ Python O(n + m) O(n) Medium
0839 Similar String Groups C++ Python O(n^2 * l) O(n) Hard Union Find
0848 Shifting Letters C++ Python O(n) O(1) Medium
0859 Buddy Strings C++ Python O(n) O(1) Easy
0880 Decoded String at Index C++ Python O(n) O(1) Medium
0884 Uncommon Words from Two Sentences C++ Python O(m + n) O(m + n) Easy
0890 Find and Replace Pattern C++ Python O(n * l) O(1) Medium
0893 Groups of Special-Equivalent Strings C++ Python O(n * l) O(n) Easy
0916 Word Subsets C++ Python O(m + n) O(1) Medium
0917 Reverse Only Letters C++ Python O(n) O(1) Easy
0925 Long Pressed Name C++ Python O(n) O(1) Easy
0929 Unique Email Addresses C++ Python O(n * l) O(n * l) Easy
0939 Minimum Area Rectangle C++ Python O(n^1.5) on average O(n) Medium
0942 DI String Match C++ Python O(n) O(1) Easy
0944 Delete Columns to Make Sorted C++ Python O(n * l) O(1) Medium
0953 Verifying an Alien Dictionary C++ Python O(n * l) O(1) Easy
0955 Delete Columns to Make Sorted II C++ Python O(n * l) O(n) Medium
1016 Binary String With Substrings Representing 1 To N C++ Python O(n^2) O(1) Medium
1023 Camelcase Matching C++ Python O(n * l) O(1) Medium
1061 Lexicographically Smallest Equivalent String C++ Python O(n) O(n) Medium πŸ”’ Union Find
1056 Confusing Number C++ Python O(logn) O(logn) Easy πŸ”’
1071 Greatest Common Divisor of Strings C++ Python O(m + n) O(1) Easy
1078 Occurrences After Bigram C++ Python O(n) O(1) Easy
1100 Find K-Length Substrings With No Repeated Characters C++ Python O(n) O(k) Medium πŸ”’
1108 Defanging an IP Address C++ Python O(n) O(1) Easy
1119 Remove Vowels from a String C++ Python O(n) O(1) Easy πŸ”’
1147 Longest Chunked Palindrome Decomposition C++ Python O(n) O(1) Hard Rabin-Karp Algorithm
1151 Minimum Swaps to Group All 1's Together C++ Python O(n) O(1) Medium πŸ”’ Sliding Window
1156 Swap For Longest Repeated Character Substring C++ Python O(n) O(1) Medium Sliding Window
1177 Can Make Palindrome from Substring C++ Python O(m + n) O(n) Medium
1178 Number of Valid Words for Each Puzzle C++ Python O(n * l + m * L) O(L!) Hard Trie, Bit Manipulation
1189 Maximum Number of Balloons C++ Python O(n) O(1) Easy Hash
1233 Remove Sub-Folders from the Filesystem C++ Python O(n) O(t) Medium Trie
1234 Replace the Substring for Balanced String C++ Python O(n) O(t) Medium Two Pointers, Sliding Window

Linked List

# Title Solution Time Space Difficulty Tag Note
0002 Add Two Numbers C++ Python O(n) O(1) Medium
0021 Merge Two Sorted Lists C++ Python O(n) O(1) Easy
0023 Merge k Sorted Lists C++ Python O(nlogk) O(1) Hard Heap, Divide and Conquer
0024 Swap Nodes in Pairs C++ Python O(n) O(1) Easy
0025 Reverse Nodes in k-Group C++ Python O(n) O(1) Hard
0061 Rotate List C++ Python O(n) O(1) Medium
0082 Remove Duplicates from Sorted List II C++ Python O(n) O(1) Medium
0083 Remove Duplicates from Sorted List C++ Python O(n) O(1) Easy
0092 Reverse Linked List II C++ Python O(n) O(1) Medium
0138 Copy List with Random Pointer C++ Python O(n) O(1) Medium
0160 Intersection of Two Linked Lists C++ Python O(m + n) O(1) Easy
0203 Remove Linked List Elements C++ Python O(n) O(1) Easy
0206 Reverse Linked List C++ Python O(n) O(1) Easy
0234 Palindrome Linked List C++ Python O(n) O(1) Easy
0237 Delete Node in a Linked List C++ Python O(1) O(1) Easy LintCode
0328 Odd Even Linked List C++ Python O(n) O(1) Medium
0369 Plus One Linked List C++ Python O(n) O(1) Medium πŸ”’ Two Pointers
0445 Add Two Numbers II C++ Python O(m + n) O(m + n) Medium
0725 Split Linked List in Parts C++ Python O(n + k) O(1) Medium
0817 Linked List Components C++ Python O(m + n) O(m) Medium
0986 Interval List Intersections C++ Python O(m + n) O(1) Medium
1171 Remove Zero Sum Consecutive Nodes from Linked List C++ Python O(n) O(n) Medium Hash
1180 Count Substrings with Only One Distinct Letter C++ Python O(n) O(1) Easy πŸ”’
1181 Before and After Puzzle C++ Python O(l * rlogr) O(l * (n + r)) Medium πŸ”’ Hash

Stack

# Title Solution Time Space Difficulty Tag Note
0020 Valid Parentheses C++ Python O(n) O(n) Easy
0032 Longest Valid Parentheses C++ Python O(n) O(1) Hard
0071 Simplify Path C++ Python O(n) O(n) Medium
0084 Largest Rectangle in Histogram C++ Python O(n) O(n) Hard Mono Stack, DP
0085 Maximal Rectangle C++ Python O(m * n) O(n) Hard EPI Mono Stack
0101 Symmetric Tree C++ Python O(n) O(h) Easy
0150 Evaluate Reverse Polish Notation C++ Python O(n) O(n) Medium
0155 Min Stack C++ Python O(n) O(1) Easy
0173 Binary Search Tree Iterator C++ Python O(1) O(h) Medium
0224 Basic Calculator C++ Python O(n) O(n) Hard
0227 Basic Calculator II C++ Python O(n) O(n) Medium
0232 Implement Queue using Stacks C++ Python O(1), amortized O(n) Easy EPI, LintCode
0255 Verify Preorder Sequence in Binary Search Tree C++ Python O(n) O(1) Medium πŸ”’
0272 Closest Binary Search Tree Value II C++ Python O(h + k) O(h) Hard πŸ”’
0331 Verify Preorder Serialization of a Binary Tree C++ Python O(n) O(1) Medium
0341 Flatten Nested List Iterator C++ Python O(n) O(h) Medium πŸ”’ Iterator
0385 Mini Parser C++ Python O(n) O(h) Medium
0394 Decode String C++ Python O(n) O(n) Medium
0439 Ternary Expression Parser C++ Python O(n) O(1) Medium πŸ”’
0456 132 Pattern C++ Python O(n) O(n) Medium
0636 Exclusive Time of Functions C++ Python O(n) O(n) Medium
0682 Baseball Game C++ Python O(n) O(n) Easy
0726 Number of Atoms C++ Python O(n) O(n) Hard
0735 Asteroid Collision C++ Python O(n) O(n) Medium
0736 Parse Lisp Expression C++ Python O(n^2) O(n^2) Hard
0739 Daily Temperatures C++ Python O(n) O(n) Medium
0770 Basic Calculator IV C++ Python add: O(d * t)
sub: O(d * t)
mul: O(d * t^2)
eval: O(d * t)
to_list: O(d * tlogt)
O(e + d * t) Hard
0772 Basic Calculator III C++ Python O(n) O(n) Hard
0853 Car Fleet C++ Python O(nlogn) O(n) Medium
0856 Score of Parentheses C++ Python O(n) O(1) Medium
0872 Leaf-Similar Trees C++ Python O(n) O(h) Easy
0895 Maximum Frequency Stack C++ Python O(1) O(n) Hard Hash
0901 Online Stock Span C++ Python O(n) O(n) Medium
0921 Minimum Add to Make Parentheses Valid C++ Python O(n) O(1) Medium
0946 Validate Stack Sequences C++ Python O(n) O(n) Medium
1003 Check If Word Is Valid After Substitutions C++ Python O(n) O(n) Medium
1019 Next Greater Node In Linked List C++ Python O(n) O(n) Medium Mono Stack
1021 Remove Outermost Parentheses C++ Python O(n) O(1) Easy
1047 Remove All Adjacent Duplicates In String C++ Python O(n) O(n) Easy
1063 Number of Valid Subarrays C++ Python O(n) O(n) Hard πŸ”’ Mono Stack
1130 Minimum Cost Tree From Leaf Values C++ Python O(n) O(n) Medium Mono Stack
1190 Reverse Substrings Between Each Pair of Parentheses C++ Python O(n^2) O(n) Medium
1209 Remove All Adjacent Duplicates in String II C++ Python O(n) O(n) Medium

Queue

# Title Solution Time Space Difficulty Tag Note
0239 Sliding Window Maximum C++ Python O(n) O(k) Hard EPI, LintCode
0281 Zigzag Iterator C++ Python O(n) O(k) Medium πŸ”’
0346 Moving Average from Data Stream C++ Python O(1) O(w) Easy πŸ”’
0862 Shortest Subarray with Sum at Least K C++ Python O(n) O(n) Hard
0933 Number of Recent Calls C++ Python O(1) on average O(w) Easy

Heap

# Title Solution Time Space Difficulty Tag Note
0264 Ugly Number II C++ Python O(n) O(1) Medium CTCI, LintCode BST, Heap
0295 Find Median from Data Stream C++ Python O(nlogn) O(n) Hard EPI, LintCode BST, Heap
0313 Super Ugly Number C++ Python O(n * k) O(n + k) Medium BST, Heap
0358 Rearrange String k Distance Apart C++ Python O(n) O(n) Hard πŸ”’ Greedy, Heap
0373 Find K Pairs with Smallest Sums C++ Python O(k * log(min(n, m, k))) O(min(n, m, k)) Medium
0378 Kth Smallest Element in a Sorted Matrix C++ Python O(k * log(min(n, m, k))) O(min(n, m, k)) Medium LintCode
0407 Trapping Rain Water II C++ Python O(m * n * (logm + logn)) O(m * n) Hard LintCode
0632 Smallest Range C++ Python O(nlogk) O(k) Hard
0703 Kth Largest Element in a Stream C++ Python O(nlogk) O(k) Easy
0846 Hand of Straights C++ Python O(nlogn) O(n) Medium
0855 Exam Room C++ Python seat: O(logn)
leave: O(logn)
O(n) Medium BST, Hash
0857 Minimum Cost to Hire K Workers C++ Python O(nlogn) O(n) Hard Sort
0871 Minimum Number of Refueling Stops C++ Python O(nlogn) O(n) Hard Sort
1046 Last Stone Weight C++ Python O(nlogn) O(n) Easy
1057 Campus Bikes C++ Python O((w * b) * log(w * b)) O(w * b) Medium πŸ”’

Tree

# Title Solution Time Space Difficulty Tag Note
0094 Binary Tree Inorder Traversal C++ Python O(n) O(1) Medium Morris Traversal
0099 Recover Binary Search Tree C++ Python O(n) O(1) Hard Morris Traversal
0144 Binary Tree Preorder Traversal C++ Python O(n) O(1) Medium Morris Traversal
0145 Binary Tree Postorder Traversal C++ Python O(n) O(1) Hard Morris Traversal
0208 Implement Trie (Prefix Tree) C++ Python O(n) O(1) Medium Trie
0211 Add and Search Word - Data structure design C++ Python O(min(n, h)) O(min(n, h)) Medium Trie, DFS
0226 Invert Binary Tree C++ Python O(n) O(h), O(w) Easy
0297 Serialize and Deserialize Binary Tree C++ Python O(n) O(h) Hard LintCode DFS
0307 Range Sum Query - Mutable C++ Python ctor: O(n), update: O(logn), query: O(logn) O(n) Medium LintCode DFS, Segment Tree, BIT, Fenwick Tree
0308 Range Sum Query 2D - Mutable C++ Python ctor: O(m * n), update: O(logm + logn), query: O(logm + logn) O(m * n) Hard πŸ”’ DFS, Segment Tree, BIT, Fenwick Tree
0315 Count of Smaller Numbers After Self C++ Python O(nlogn) O(n) Hard LintCode BST, BIT, Fenwick Tree, Divide and Conquer
0525 Contiguous Array C++ Python O(n) O(n) Medium
0529 Minesweeper C++ Python O(m * n) O(m + n) Medium
0536 Construct Binary Tree from String C++ Python O(n) O(h) Medium πŸ”’
0538 Convert BST to Greater Tree C++ Python O(n) O(h) Easy
0543 Diameter of Binary Tree C++ Python O(n) O(h) Easy
0545 Boundary of Binary Tree C++ Python O(n) O(h) Medium πŸ”’
0548 Split Array with Equal Sum C++ Python O(n^2) O(n) Medium πŸ”’
0563 Binary Tree Tilt C++ Python O(n) O(n) Easy
0572 Subtree of Another Tree C++ Python O(m * n) O(h) Easy
0606 Construct String from Binary Tree C++ Python O(n) O(h) Easy
0617 Merge Two Binary Trees C++ Python O(n) O(h) Easy
0623 Add One Row to Tree C++ Python O(n) O(h) Medium
0637 Average of Levels in Binary Tree C++ Python O(n) O(h) Easy
0652 Find Duplicate Subtrees C++ Python O(n) O(n) Medium DFS, Hash
0653 Two Sum IV - Input is a BST C++ Python O(n) O(h) Easy Two Pointers
0654 Maximum Binary Tree C++ Python O(n) O(n) Medium LintCode Mono Stack
0655 Print Binary Tree C++ Python O(n) O(h) Medium
0662 Maximum Width of Binary Tree C++ Python O(n) O(h) Medium DFS
0663 Equal Tree Partition C++ Python O(n) O(n) Medium πŸ”’ Hash
0677 Map Sum Pairs C++ Python O(n) O(t) Medium Trie
0684 Redundant Connection C++ Python O(n) O(n) Medium Union Find
0685 Redundant Connection II C++ Python O(n) O(n) Hard Union Find
0687 Longest Univalue Path C++ Python O(n) O(h) Easy
0699 Falling Squares C++ Python O(nlogn) O(n) Hard Segment Tree
0814 Binary Tree Pruning C++ Python O(n) O(h) Medium DFS
0850 Rectangle Area II C++ Python O(nlogn) O(n) Hard Segment Tree
0863 All Nodes Distance K in Binary Tree C++ Python O(n) O(n) Medium DFS + BFS
0866 Smallest Subtree with all the Deepest Nodes C++ Python O(n) O(h) Medium DFS
0889 Construct Binary Tree from Preorder and Postorder Traversal C++ Python O(n) O(h) Medium DFS, stack
0897 Increasing Order Search Tree C++ Python O(n) O(h) Easy DFS
0919 Complete Binary Tree Inserter C++ Python ctor: O(n)
insert: O(1)
get_root: O(1)
O(n) Medium
0938 Range Sum of BST C++ Python O(n) O(h) Medium DFS
0951 Flip Equivalent Binary Trees C++ Python O(n) O(h) Medium DFS
0958 Check Completeness of a Binary Tree C++ Python O(n) O(w) Medium BFS
0965 Univalued Binary Tree C++ Python O(n) O(h) Easy DFS
0971 Flip Binary Tree To Match Preorder Traversal C++ Python O(n) O(h) Medium DFS
0979 Distribute Coins in Binary Tree C++ Python O(n) O(h) Medium DFS
0987 Vertical Order Traversal of a Binary Tree C++ Python O(nlogn) O(n) Medium DFS
0988 Smallest String Starting From Leaf C++ Python O(n + l * h) O(h) Medium DFS
0993 Cousins in Binary Tree C++ Python O(n) O(h) Easy DFS
0998 Maximum Binary Tree II C++ Python O(h) O(1) Medium
1008 Construct Binary Search Tree from Preorder Traversal C++ Python O(n) O(h) Medium
1022 Sum of Root To Leaf Binary Numbers C++ Python O(n) O(h) Easy
1026 Maximum Difference Between Node and Ancestor C++ Python O(n) O(h) Medium DFS
1028 Recover a Tree From Preorder Traversal C++ Python O(n) O(h) Hard DFS
1032 Stream of Characters C++ C++ Python Python ctor: O(n)
query: O(m)
O(t) Hard Aho-Corasick Automata, Trie
1038 Binary Search Tree to Greater Sum Tree C++ Python O(n) O(h) Medium DFS
1065 Index Pairs of a String C++ Python O(n + m + z) O(t) Easy πŸ”’ Aho-Corasick Automata, Trie
1080 Insufficient Nodes in Root to Leaf Paths C++ Python O(n) O(h) Medium DFS
1104 Path In Zigzag Labelled Binary Tree C++ Python O(logn) O(logn) Easy Math
1120 Maximum Average Subtree C++ Python O(n) O(h) Easy πŸ”’ DFS
1123 Lowest Common Ancestor of Deepest Leaves C++ Python O(n) O(h) Medium DFS
1145 Binary Tree Coloring Game C++ Python O(n) O(h) Medium DFS

Hash Table

# Title Solution Time Space Difficulty Tag Note
0001 Two Sum C++ Python O(n) O(n) Easy
0003 Longest Substring Without Repeating Characters C++ Python O(n) O(1) Medium
0030 Substring with Concatenation of All Words C++ Python O((m + n) * k) O(n * k) Hard
0036 Valid Sudoku C++ Python O(9^2) O(9) Easy
0049 Group Anagrams C++ Python O(n * glogg) O(n) Medium
0076 Minimum Window Substring C++ Python O(n) O(k) Hard
0149 Max Points on a Line C++ Python O(n^2) O(n) Hard
0159 Longest Substring with At Most Two Distinct Characters C++ Python O(n) O(1) Hard πŸ”’
0170 Two Sum III - Data structure design C++ Python O(n) O(n) Easy πŸ”’
0187 Repeated DNA Sequences Python O(n) O(n) Medium
0202 Happy Number C++ Python O(k) O(k) Easy
0204 Count Primes C++ Python O(n) O(n) Easy
0205 Isomorphic Strings C++ Python O(n) O(1) Easy
0217 Contains Duplicate C++ Python O(n) O(n) Easy
0219 Contains Duplicate II C++ Python O(n) O(n) Easy
0244 Shortest Word Distance II C++ Python ctor: O(n), lookup: O(a + b) O(n) Medium πŸ”’
0246 Strobogrammatic Number C++ Python O(n) O(1) Easy πŸ”’
0249 Group Shifted Strings C++ Python O(nlogn) O(n) Easy πŸ”’
0266 Palindrome Permutation C++ Python O(n) O(1) Easy πŸ”’
0288 Unique Word Abbreviation C++ Python ctor: O(n), lookup: O(1) O(k) Easy πŸ”’
0290 Word Pattern C++ Python O(n) O(c) Easy variant of Isomorphic Strings
0299 Bulls and Cows C++ Python O(n) O(1) Easy
0305 Number of Islands II C++ Python O(k) O(k) Hard LintCode, πŸ”’ Union Find
0314 Binary Tree Vertical Order Traversal C++ Python O(n) O(n) Medium πŸ”’ BFS
0323 Number of Connected Components in an Undirected Graph C++ Python O(n) O(n) Medium πŸ”’ Union Find
0325 Maximum Size Subarray Sum Equals k C++ Python O(n) O(n) Medium πŸ”’
0336 Palindrome Pairs C++ Python O(n * k^2) O(n * k) Hard
0340 Longest Substring with At Most K Distinct Characters C++ Python O(n) O(1) Hard πŸ”’
0356 Line Reflection C++ Python O(n) O(n) Medium πŸ”’ Hash, Two Pointers
0387 First Unique Character in a String C++ Python O(n) O(n) Easy
0388 Longest Absolute File Path C++ Python O(n) O(d) Medium Stack
0409 Longest Palindrome C++ Python O(n) O(1) Easy
0438 Find All Anagrams in a String C++ Python O(n) O(1) Easy
0447 Number of Boomerangs C++ Python O(n^2) O(n) Easy
0454 4Sum II C++ Python O(n^2) O(n^2) Medium
0470 Implement Rand10() Using Rand7() C++ Python O(1) O(1) Medium
0473 Matchsticks to Square C++ Python O(n * s * 2^n) O(n * (2^n + s)) Medium
0523 Continuous Subarray Sum C++ Python O(n) O(k) Medium
0532 K-diff Pairs in an Array C++ Python O(n) O(n) Easy
0554 Brick Wall C++ Python O(n) O(m) Medium
0560 Subarray Sum Equals K C++ Python O(n) O(n) Medium
0561 Array Partition I C++ Python O(r) O(r) Easy
0575 Distribute Candies C++ Python O(n) O(n) Easy
0594 Longest Harmonious Subsequence C++ Python O(n) O(n) Easy
0599 Minimum Index Sum of Two Lists C++ Python O((m + n) * l) O(m * l) Easy
0609 Find Duplicate File in System C++ Python O(n * l) O(n * l) Medium
0721 Accounts Merge C++ Python O(nlogn) O(n) Medium Union Find
0734 Sentence Similarity C++ Python O(n + p) O(p) Easy
0737 Sentence Similarity II C++ Python O(n + p) O(p) Medium Union Find
0748 Shortest Completing Word C++ Python O(n) O(1) Easy
0760 Find Anagram Mappings C++ Python O(n) O(n) Easy
0771 Jewels and Stones C++ Python O(m + n) O(n) Easy
0811 Subdomain Visit Count C++ Python O(n) O(n) Easy
0822 Card Flipping Game C++ Python O(n) O(n) Medium
0825 Friends Of Appropriate Ages C++ Python O(a^2 + n) O(a) Medium
0869 Reordered Power of 2 C++ Python O(1) O(1) Medium
0873 Length of Longest Fibonacci Subsequence C++ Python O(n^2) O(n) Medium
0957 Prison Cells After N Days C++ Python O(1) O(1) Medium
0966 Vowel Spellchecker C++ Python O(n) O(w) Medium
0974 Subarray Sums Divisible by K C++ Python O(n) O(k) Medium variant of Subarray Sum Equals K
0982 Triples with Bitwise AND Equal To Zero C++ Python O(nlogn) O(n) Hard Math, Fast Wavelet Transform (FWT)
0992 Subarrays with K Different Integers C++ Python O(n) O(k) Hard Two Pointers
1001 Grid Illumination C++ Python O(l + q) O(l) Hard
1124 Longest Well-Performing Interval C++ Python O(n) O(n) Medium
1133 Largest Unique Number C++ Python O(n) O(n) Easy πŸ”’ Hash
1152 Analyze User Website Visit Pattern C++ Python O(n^3) O(n^3) Medium πŸ”’ Hash
1153 String Transforms Into Another String C++ Python O(n) O(1) Hard πŸ”’ Hash
1160 Find Words That Can Be Formed by Characters C++ Python O(m * n) O(1) Easy
1165 Single-Row Keyboard C++ Python O(n) O(1) Easy πŸ”’
1198 Find Smallest Common Element in All Rows C++ Python O(m * n) O(n) Medium πŸ”’
1207 Unique Number of Occurrences C++ Python O(n) O(n) Easy
1224 Maximum Equal Frequency C++ Python O(n) O(n) Hard

Math

# Title Solution Time Space Difficulty Tag Note
0007 Reverse Integer C++ Python O(1) O(1) Easy
0009 Palindrome Number C++ Python O(1) O(1) Easy
0012 Integer to Roman C++ Python O(n) O(1) Medium
0013 Roman to Integer C++ Python O(n) O(1) Easy
0029 Divide Two Integers C++ Python O(1) O(1) Medium
0050 Pow(x, n) C++ Python O(1) O(1) Medium
0060 Permutation Sequence C++ Python O(n^2) O(n) Medium Cantor Ordering
0065 Valid Number C++ Python O(n) O(1) Hard Automata
0089 Gray Code C++ Python O(2^n) O(1) Medium
0166 Fraction to Recurring Decimal C++ Python O(logn) O(1) Medium
0168 Excel Sheet Column Title C++ Python O(logn) O(1) Easy
0171 Excel Sheet Column Number C++ Python O(n) O(1) Easy
0172 Factorial Trailing Zeroes C++ Python O(1) O(1) Easy
0223 Rectangle Area C++ Python O(1) O(1) Easy
0233 Number of Digit One C++ Python O(1) O(1) Hard CTCI, LintCode
0248 Strobogrammatic Number III C++ Python O(5^(n/2)) O(n) Hard πŸ”’
0258 Add Digits C++ Python O(1) O(1) Easy
0263 Ugly Number C++ Python O(1) O(1) Easy
0292 Nim Game C++ Python O(1) O(1) Easy LintCode
0319 Bulb Switcher C++ Python O(1) O(1) Medium
0326 Power of Three C++ Python O(1) O(1) Easy
0335 Self Crossing C++ Python O(n) O(1) Hard
0338 Counting Bits C++ Python O(n) O(n) Medium
0343 Integer Break C++ Python O(logn) O(1) Medium Tricky, DP
0365 Water and Jug Problem C++ Python O(logn) O(1) Medium BΓ©zout's identity
0372 Super Pow C++ Python O(n) O(1) Medium
0382 Linked List Random Node C++ Python O(n) O(1) Medium Reservoir Sampling
0386 Lexicographical Numbers C++ Python O(n) O(1) Medium
0390 Elimination Game C++ Python O(logn) O(1) Medium
0391 Perfect Rectangle C++ Python O(n) O(n) Hard
0398 Random Pick Index C++ Python O(n) O(1) Medium Reservoir Sampling
0400 Nth Digit C++ Python O(logn) O(1) Easy
0413 Arithmetic Slices C++ Python O(n) O(1) Medium
0423 Reconstruct Original Digits from English C++ Python O(n) O(1) Medium GCJ2016 - Round 1B
0441 Arranging Coins C++ Python O(nlogn) O(1) Easy Binary Search
0453 Minimum Moves to Equal Array Elements C++ Python O(n) O(1) Easy
0458 Poor Pigs C++ Python O(n) O(1) Easy
0469 Convex Polygon C++ Python O(n) O(1) Medium πŸ”’
0470 Implement Rand10() Using Rand7() C++ Python O(1) O(1) Medium
0478 Generate Random Point in a Circle C++ Python O(1) O(1) Medium
0497 Random Point in Non-overlapping Rectangles C++ Python ctor: O(n)
pick: O(logn)
O(n) Medium
0517 Super Washing Machines C++ Python O(n) O(1) Hard
0519 Random Flip Matrix C++ Python ctor: O(1)
pick: O(1) reset: O(n)
O(n) Medium
0528 Random Pick with Weight C++ Python ctor: O(n)
pick: O(logn)
O(n) Medium
0537 Complex Number Multiplication C++ Python O(1) O(1) Medium
0553 Optimal Division C++ Python O(n) O(1) Medium
0573 Squirrel Simulation C++ Python O(n) O(1) Medium πŸ”’
0592 Fraction Addition and Subtraction C++ Python O(nlogx) O(n) Medium
0593 Valid Square C++ Python O(1) O(1) Medium
0598 Range Addition II C++ Python O(p) O(1) Easy
0625 Minimum Factorization C++ Python O(loga) O(1) Medium πŸ”’
0628 Maximum Product of Three Numbers C++ Python O(n) O(1) Easy
0633 Sum of Square Numbers C++ Python O(sqrt(c) * logc) O(1) Easy
0634 Find the Derangement of An Array C++ Python O(n) O(1) Medium πŸ”’
0640 Solve the Equation C++ Python O(n) O(n) Medium
0651 4 Keys Keyboard C++ Python O(1) O(1) Medium πŸ”’ Math, DP
0660 Remove 9 C++ Python O(logn) O(1) Hard πŸ”’
0672 Bulb Switcher II C++ Python O(1) O(1) Medium
0728 Self Dividing Numbers C++ Python O(n) O(1) Medium
0754 Reach a Number C++ Python O(logn) O(1) Medium
0775 Global and Local Inversions C++ Python O(n) O(1) Medium
0779 K-th Symbol in Grammar C++ Python O(1) O(1) Medium
0780 Reaching Points C++ Python O(log(max(m, n))) O(1) Hard
0781 Rabbits in Forest C++ Python O(n) O(n) Medium
0782 Transform to Chessboard C++ Python O(n^2) O(n) Hard
0789 Escape The Ghosts C++ Python O(n) O(1) Medium
0800 Similar RGB Color C++ Python O(1) O(1) Easy πŸ”’
0810 Chalkboard XOR Game C++ Python O(1) O(1) Hard
0812 Largest Triangle Area C++ Python O(n^3) O(1) Easy
0829 Consecutive Numbers Sum C++ Python O(sqrt(n)) O(1) Medium
0836 Rectangle Overlap C++ Python O(1) O(1) Easy
0858 Mirror Reflection C++ Python O(1) O(1) Medium
0867 Prime Palindrome C++ Python O(n^(1/2) * (logn + n^(1/2))) O(logn) Medium
0883 Projection Area of 3D Shapes C++ Python O(n^2) O(1) Easy
0887 Super Egg Drop C++ Python O(klogn) O(1) Hard
0891 Sum of Subsequence Widths C++ Python O(n) O(1) Hard
0899 Orderly Queue C++ Python O(n^2) O(n) Hard
0902 Numbers At Most N Given Digit Set C++ Python O(logn) O(logn) Hard
0906 Super Palindromes C++ Python O(n^0.25 * logn) O(logn) Hard
0907 Sum of Subarray Minimums C++ Python O(n) O(n) Medium Mono Stack
0908 Smallest Range I C++ Python O(n) O(1) Easy
0910 Smallest Range II C++ Python O(nlogn) O(1) Medium
0914 X of a Kind in a Deck of Cards C++ Python O(n * (logn)^2) O(n) Easy
0963 Minimum Area Rectangle II C++ Python O(n^2) ~ O(n^3) O(n^2) Medium
0970 Powerful Integers C++ Python O((logn)^2) O(r) Easy
0972 Equal Rational Numbers C++ Python O(1) O(1) Hard
1006 Clumsy Factorial C++ Python O(1) O(1) Medium
1009 Complement of Base 10 Integer C++ Python O(logn) O(1) Easy
1012 Numbers With Repeated Digits C++ Python O(logn) O(logn) Hard
1015 Smallest Integer Divisible by K C++ Python O(k) O(1) Medium
1017 Convert to Base -2 C++ Python O(logn) O(1) Medium
1025 Divisor Game C++ Python O(1) O(1) Easy DP
1037 Valid Boomerang C++ Python O(1) O(1) Easy
1041 Robot Bounded In Circle C++ Python O(n) O(1) Medium
1067 Digit Count in Range C++ Python O(logn) O(1) Hard πŸ”’, variant of Number of Digit One
1073 Adding Two Negabinary Numbers C++ Python O(n) O(n) Medium
1079 Letter Tile Possibilities C++ Python O(n^2) O(n) Medium Generating Function, Backtracking
1088 Confusing Number II C++ Python O(logn) O(logn) Hard πŸ”’
1103 Distribute Candies to People C++ Python O(n + logc) O(1) Easy Binary Search
1118 Number of Days in a Month C++ Python O(1) O(1) Easy πŸ”’
1121 Divide Array Into Increasing Sequences C++ Python O(n) O(1) Hard πŸ”’
1128 Number of Equivalent Domino Pairs C++ Python O(n) O(n) Easy
1131 Maximum of Absolute Value Expression C++ Python O(n) O(1) Medium
1134 Armstrong Number C++ Python O(klogk) O(k) Easy πŸ”’
1150 Check If a Number Is Majority Element in a Sorted Array C++ Python O(nlogn) O(1) Easy πŸ”’ Binary Search
1157 Online Majority Element In Subarray C++ Python ctor: O(n)
query: O(klogn)
O(n) Hard Binary Search, Segment Tree, Boyer–Moore Majority Vote Algorithm
1154 Day of the Year C++ Python O(1) O(1) Easy
1175 Prime Arrangements C++ Python O(n) O(n) Easy
1185 Day of the Week C++ Python O(1) O(1) Easy Zeller Formula
1197 Minimum Knight Moves C++ Python O(1) O(1) Medium πŸ”’ DP, Math
1217 Play with Chips C++ Python O(n) O(1) Medium
1227 Airplane Seat Assignment Probability C++ Python O(1) O(1) Medium
1232 Check If It Is a Straight Line C++ Python O(1) O(1) Easy
1237 Find Positive Integer Solution for a Given Equation C++ Python O(n) O(1) Easy
1238 Circular Permutation in Binary Representation C++ Python O(2^n) O(1) Medium variant of Gray Code
1250 Check If It Is a Good Array C++ Python O(nlogn) O(1) Hard BΓ©zout's identity

Sort

# Title Solution Time Space Difficulty Tag Note
0056 Merge Intervals C++ Python O(nlogn) O(1) Hard
0057 Insert Interval C++ Python O(n) O(1) Hard
0075 Sort Colors C++ Python O(n) O(1) Medium Tri Partition
0088 Merge Sorted Array C++ Python O(n) O(1) Easy
0147 Insertion Sort List C++ Python O(n^2) O(1) Medium
0148 Sort List C++ Python O(nlogn) O(logn) Medium
0164 Maximum Gap C++ Python O(n) O(n) Hard Tricky
0179 Largest Number C++ Python O(nlogn) O(1) Medium
0218 The Skyline Problem C++ Python O(nlogn) O(n) Hard Sort, BST
0252 Meeting Rooms C++ Python O(nlogn) O(n) Easy πŸ”’
0253 Meeting Rooms II C++ Python O(nlogn) O(n) Medium πŸ”’
0274 H-Index C++ Python O(n) O(n) Medium Counting Sort
0280 Wiggle Sort C++ Python O(n) O(1) Medium πŸ”’
0324 Wiggle Sort II C++ Python O(n) on average O(1) Medium variant of Sort Colors Tri Partition
0347 Top K Frequent Elements C++ Python O(n) O(n) Medium Quick Select, Heap, Bucket Sort
0406 Queue Reconstruction by Height C++ Python O(n * sqrt(n)) O(n) Medium Tricky
0451 Sort Characters By Frequency C++ Python O(n) O(n) Medium
0692 Top K Frequent Words C++ Python O(n + klogk) on average O(n) Medium Quick Select, Heap, Bucket Sort
0912 Sort an Array C++ Python O(nlogn) O(n) Medium Merge Sort, Quick Sort
0937 Reorder Log Files C++ Python O(nlogn * l) O(l) Easy
0969 Pancake Sorting C++ Python O(n^2) O(l) Medium
0973 K Closest Points to Origin C++ Python O(n) on average O(1) Easy Quick Select, Heap
0976 Largest Perimeter Triangle C++ Python O(nlogn) O(1) Easy
1054 Distant Barcodes C++ Python O(klogk) O(k) Medium variant of Rearrange String k Distance Apart
1086 High Five C++ Python O(nlogn) O(n) Easy πŸ”’
1094 Car Pooling C++ Python O(nlogn) O(n) Medium variant of Meeting Rooms II
1122 Relative Sort Array C++ Python O(nlogn) O(n) Easy
1229 Meeting Scheduler C++ Python O(nlogn) O(n) Medium Line Sweep, Heap

Two Pointers

# Title Solution Time Space Difficulty Tag Note
0019 Remove Nth Node From End of List C++ Python O(n) O(1) Medium
0086 Partition List C++ Python O(n) O(1) Medium
0141 Linked List Cycle C++ Python O(n) O(1) Easy
0142 Linked List Cycle II C++ Python O(n) O(1) Medium
0143 Reorder List C++ Python O(n) O(1) Medium
0167 Two Sum II - Input array is sorted C++ Python O(n) O(1) Medium
0259 3Sum Smaller C++ Python O(n^2) O(1) Medium πŸ”’, LintCode
0283 Move Zeroes C++ Python O(n) O(1) Easy
0287 Find the Duplicate Number C++ Python O(n) O(1) Hard Binary Search, Two Pointers
0344 Reverse String C++ Python O(n) O(1) Easy
0345 Reverse Vowels of a String C++ Python O(n) O(1) Easy
0349 Intersection of Two Arrays C++ Python O(m + n) O(min(m, n)) Easy EPI Hash, Binary Search
0350 Intersection of Two Arrays II C++ Python O(m + n) O(1) Easy EPI Hash, Binary Search
0360 Sort Transformed Array C++ Python O(n) O(1) Medium πŸ”’
0457 Circular Array Loop C++ Python O(n) O(1) Medium
0567 Permutation in String C++ Python O(n) O(1) Medium
0611 Valid Triangle Number C++ Python O(n^2) O(1) Medium
0777 Swap Adjacent in LR String C++ Python O(n) O(1) Medium
0826 Most Profit Assigning Work C++ Python O(mlogm + nlogn) O(n) Medium
0828 Unique Letter String C++ Python O(n) O(1) Hard
0844 Backspace String Compare C++ Python O(m + n) O(1) Easy
0876 Middle of the Linked List C++ Python O(n) O(1) Easy
0904 Fruit Into Baskets C++ Python O(n) O(1) Medium
0930 Binary Subarrays With Sum C++ Python O(n) O(1) Medium
0977 Squares of a Sorted Array C++ Python O(n) O(1) Easy
1004 Max Consecutive Ones III C++ Python O(n) O(1) Medium
1033 Moving Stones Until Consecutive C++ Python O(1) O(1) Easy
1040 Moving Stones Until Consecutive II C++ Python O(nlogn) O(1) Medium
1213 Intersection of Three Sorted Arrays C++ Python O(n) O(1) Easy πŸ”’
1214 Two Sum BSTs C++ Python O(n) O(n) Medium πŸ”’ Stack
1248 Count Number of Nice Subarrays C++ Python O(n) O(k) Medium variant of Subarrays with K Different Integers Two Pointers, Sliding Window

Recursion

# Title Solution Time Space Difficulty Tag Note
0095 Unique Binary Search Trees II C++ Python O(4^n / n^(3/2) O(4^n / n^(3/2) Medium
0098 Validate Binary Search Tree C++ Python O(n) O(1) Medium
0100 Same Tree C+ Python O(n) O(h) Easy
0104 Maximum Depth of Binary Tree C++ Python O(n) O(h) Easy
0105 Construct Binary Tree from Preorder and Inorder Traversal C++ Python O(n) O(n) Medium
0106 Construct Binary Tree from Inorder and Postorder Traversal C++ Python O(n) O(n) Medium
0108 Convert Sorted Array to Binary Search Tree C++ Python O(n) O(logn) Medium
0109 Convert Sorted List to Binary Search Tree C++ Python O(n) O(logn) Medium
0110 Balanced Binary Tree Python O(n) O(h) Easy
0111 Minimum Depth of Binary Tree Python O(n) O(h) Easy
0114 Flatten Binary Tree to Linked List Python O(n) O(h) Medium
0116 Populating Next Right Pointers in Each Node Python O(n) O(1) Medium
0124 Binary Tree Maximum Path Sum Python O(n) O(h) Hard
0129 Sum Root to Leaf Numbers Python O(n) O(h) Medium
0156 Binary Tree Upside Down Python O(n) O(1) Medium πŸ”’
0241 Different Ways to Add Parentheses C++ Python O(n * 4^n / n^(3/2)) O(n * 4^n / n^(3/2)) Medium
0298 Binary Tree Longest Consecutive Sequence C++ Python O(n) O(h) Medium πŸ”’
0327 Count of Range Sum C++ Python O(nlogn) O(n) Hard
0333 Largest BST Subtree C++ Python O(n) O(h) Medium πŸ”’
0337 House Robber III C++ Python O(n) O(h) Medium
0395 Longest Substring with At Least K Repeating Characters C++ Python O(n) O(1) Medium
0404 Sum of Left Leaves C++ Python O(n) O(h) Easy
0437 Path Sum III C++ Python O(n) O(h) Easy
0544 Output Contest Matches C++ Python O(n) O(n) Medium
0549 Binary Tree Longest Consecutive Sequence II C++ Python O(n) O(h) Medium πŸ”’
0669 Trim a Binary Search Tree C++ Python O(n) O(h) Easy
0671 Second Minimum Node In a Binary Tree C++ Python O(n) O(h) Easy
0761 Special Binary String C++ Python O(n^2) O(n) Hard
1106 Parsing A Boolean Expression C++ Python O(n) O(n) Hard

Binary Search

# Title Solution Time Space Difficulty Tag Note
0004 Median of Two Sorted Arrays C++ Python O(log(min(m, n))) O(1) Hard
0033 Search in Rotated Sorted Array C++ Python O(logn) O(1) Hard
0034 Search for a Range C++ Python O(logn) O(1) Medium
0035 Search Insert Position C++ Python O(logn) O(1) Medium
0069 Sqrt(x) C++ Python O(logn) O(1) Medium
0074 Search a 2D Matrix C++ Python O(logm + logn) O(1) Medium
0081 Search in Rotated Sorted Array II C++ Python O(logn) O(1) Medium
0153 Find Minimum in Rotated Sorted Array C++ Python O(logn) O(1) Medium
0154 Find Minimum in Rotated Sorted Array II C++ Python O(logn) ~ O(n) O(1) Hard
0162 Find Peak Element C++ Python O(logn) O(1) Medium
0222 Count Complete Tree Nodes C++ Python O((logn)^2) O(1) Medium
0275 H-Index II C++ Python O(logn) O(1) Medium Binary Search
0278 First Bad Version C++ Python O(logn) O(1) Easy LintCode
0300 Longest Increasing Subsequence C++ Python O(nlogn) O(n) Medium CTCI, LintCode Binary Search, DP
0302 Smallest Rectangle Enclosing Black Pixels C++ Python O(nlogn) O(1) Hard πŸ”’
0354 Russian Doll Envelopes C++ Python O(nlogn) O(1) Hard
0363 Max Sum of Rectangle No Larger Than K C++ Python O(min(m, n)^2 * max(m, n) * logn(max(m, n))) O(max(m, n)) Hard
0367 Valid Perfect Square C++ Python O(logn) O(1) Medium
0374 Guess Number Higher or Lower C++ Python O(logn) O(1) Easy
0410 Split Array Largest Sum C++ Python O(nlogs) O(1) Hard
0436 Find Right Interval C++ Python O(nlogn) O(n) Medium
0475 Heaters C++ Python O((m + n) * logn) O(1) Easy
0540 Single Element in a Sorted Array C++ Python O(logn) O(1) Medium
0658 Find K Closest Elements C++ Python O(logn + k) O(1) Medium
0668 Kth Smallest Number in Multiplication Table C++ Python O(m * log(m * n)) O(1) Hard
0719 Find K-th Smallest Pair Distance C++ Python O(nlogn + nlogw) O(1) Hard
0744 Find Smallest Letter Greater Than Target C++ Python O(logn) O(1) Easy
0774 Minimize Max Distance to Gas Station C++ Python O(nlogr) O(1) Hard
0786 K-th Smallest Prime Fraction C++ Python O(nlogr) O(1) Hard
0793 Preimage Size of Factorial Zeroes Function C++ Python O((logn)^2) O(1) Hard
0852 Peak Index in a Mountain Array C++ Python O(logn) O(1) Easy
0864 Random Pick with Blacklist C++ Python ctor: O(b)
pick: O(1)
O(b) Hard
0875 Koko Eating Bananas C++ Python O(nlogr) O(1) Medium
0878 Nth Magical Number C++ Python O(logn) O(1) Hard
0894 All Possible Full Binary Trees C++ Python O(n * 4^n / n^(3/2)) O(n * 4^n / n^(3/2)) Medium
0911 Online Election C++ Python ctor: O(n)
query : O(logn)
O(n) Medium
0981 Time Based Key-Value Store C++ Python set: O(1)
get : O(logn)
O(n) Medium
1011 Capacity To Ship Packages Within D Days C++ Python O(nlogr) O(1) Medium
1044 Longest Duplicate Substring C++ Python O(nlogn) O(n) Hard Rabin-Karp Algorithm
1060 Missing Element in Sorted Array C++ Python O(logn) O(1) Medium πŸ”’
1062 Longest Repeating Substring C++ Python O(nlogn) O(n) Medium πŸ”’ Rabin-Karp Algorithm
1064 Fixed Point C++ Python O(logn) O(1) Easy πŸ”’
1095 Find in Mountain Array C++ Python O(logn) O(1) Hard
1110 Delete Nodes And Return Forest C++ Python O(n) O(h + d) Medium
1170 Compare Strings by Frequency of the Smallest Character C++ Python O((m + n)logn) O(n) Easy
1201 Ugly Number III C++ Python O(logn) O(1) Medium Inclusion-Exclusion Principle
1228 Missing Number In Arithmetic Progression C++ Python O(logn) O(1) Easy
1231 Divide Chocolate C++ Python O(nlogn) O(1) Hard

Binary Search Tree

# Title Solution Time Space Difficulty Tag Note
0220 Contains Duplicate III C++ Python O(nlogk) O(k) Medium
0230 Kth Smallest Element in a BST C++ Python O(max(h, k)) O(min(h, k)) Medium
0235 Lowest Common Ancestor of a Binary Search Tree C++ Python O(h) O(1) Easy EPI
0270 Closest Binary Search Tree Value C++ Python O(h) O(1) Easy πŸ”’
0285 Inorder Successor in BST C++ Python O(h) O(1) Medium πŸ”’
0352 Data Stream as Disjoint Intervals C++ Python O(logn) O(n) Hard
0449 Serialize and Deserialize BST C++ Python O(n) O(h) Medium
0450 Delete Node in a BST C++ Python O(h) O(h) Medium
0530 Minimum Absolute Difference in BST C++ Python O(n) O(h) Easy
0776 Split BST C++ Python O(n) O(h) Medium πŸ”’
0783 Minimum Distance Between BST Nodes C++ Python O(n) O(h) Easy
0510 Inorder Successor in BST II C++ Python O(h) O(1) Medium πŸ”’

Breadth-First Search

# Title Solution Time Space Difficulty Tag Note
0102 Binary Tree Level Order Traversal C++ Python O(n) O(n) Easy
0107 Binary Tree Level Order Traversal II C++ Python O(n) O(n) Easy
0103 Binary Tree Zigzag Level Order Traversal Python O(n) O(n) Medium
0117 Populating Next Right Pointers in Each Node II Python O(n) O(1) Hard
0127 Word Ladder Python O(n * d) O(d) Medium
0130 Surrounded Regions C++ Python O(m * n) O(m + n) Medium
0133 Clone Graph Python O(n) O(n) Medium
0207 Course Schedule Python O(|V| + |E|) O(|E|) Medium Topological Sort
0210 Course Schedule II Python O(|V| + |E|) O(|E|) Medium Topological Sort
0261 Graph Valid Tree C++ Python O(|V| + |E|) O(|V| + |E|) Medium πŸ”’
0269 Alien Dictionary C++ Python O(n) O(1) Hard πŸ”’ Topological Sort, BFS, DFS
0286 Walls and Gates C++ Python O(m * n) O(g) Medium πŸ”’
0310 Minimum Height Trees C++ Python O(n) O(n) Medium
0317 Shortest Distance from All Buildings C++ Python O(k * m * n) O(m * n) Hard πŸ”’
0433 Minimum Genetic Mutation C++ Python O(n * b) O(b) Medium
0444 Sequence Reconstruction C++ Python O(n * s) O(n) Medium πŸ”’ Topological Sort
0490 The Maze C++ Python O(max(r, c) * w) O(w) Medium
0499 The Maze III C++ Python O(max(r, c) * wlogw) O(w^2) Hard
0505 The Maze II C++ Python O(max(r, c) * wlogw) O(w) Medium
0542 01 Matrix C++ Python O(m * n) O(m * n) Medium DP
0666 Path Sum IV C++ Python O(n) O(w) Medium πŸ”’ Topological Sort
0675 Cut Off Trees for Golf Event C++ Python O(t * m * n) O(m * n) Hard A* Search Algorithm
0742 Closest Leaf in a Binary Tree C++ Python O(n) O(n) Medium
0743 Network Delay Time C++ Python O(|E| * log|V|) O(|E|) Medium Dijkstra's algorithm
0752 Open the Lock C++ Python O(k * n^k + d) O(k * n^k + d) Medium
0773 Sliding Puzzle C++ Python O((m * n) * (m * n)!) O((m * n) * (m * n)!) Hard A* Search Algorithm
0787 Cheapest Flights Within K Stops C++ Python O(|E| * log|V|) O(|E|) Medium Dijkstra's algorithm
0815 Bus Routes C++ Python O(|E| + |V|) O(|E| + |V|) Hard
0854 K-Similar Strings C++ Python O(n * n!/(c_a!*...*c_z!)) O(n * n!/(c_a!*...*c_z!)) Hard
0865 Shortest Path to Get All Keys C++ Python O(k * r * c + k^3*2^k) O(k*2^k) Hard Dijkstra's algorithm
0882 Reachable Nodes In Subdivided Graph C++ Python O(|E| * log|V|) O(|E|) Hard Dijkstra's algorithm
0886 Possible Bipartition C++ Python O(|V| + |E|) O(|V| + |E|) Medium
0934 Shortest Bridge C++ Python O(n^2) O(n^2) Medium BFS, DFS
0967 Numbers With Same Consecutive Differences C++ Python O(2^n) O(2^n) Medium
0994 Rotting Oranges C++ Python O(m * n) O(m * n) Easy
1034 Coloring A Border C++ Python O(m * n) O(m + n) Medium
1036 Escape a Large Maze C++ Python O(n^2) O(n) Hard
1091 Shortest Path in Binary Matrix C++ Python O(n^2) O(n) Medium
1102 Path With Maximum Minimum Value C++ Python O((m * n) * log(m * n)) O(m * n) Medium πŸ”’ Binary Search, DFS, Dijkstra's algorithm
1129 Shortest Path with Alternating Colors C++ Python O(n + e) O(n + e) Medium
1136 Parallel Courses C++ Python O(|V| + |E|) O(|E|) Hard πŸ”’ Topological Sort
1161 Maximum Level Sum of a Binary Tree C++ Python O(n) O(w) Medium DFS
1162 As Far from Land as Possible C++ Python O(m * n) O(m * n) Medium
1163 Last Substring in Lexicographical Order C++ Python O(n) O(n) Hard
1203 Sort Items by Groups Respecting Dependencies C++ Python O(n + e) O(n + e) Hard Topological Sort
1210 Minimum Moves to Reach Target with Rotations C++ Python O(n) O(n) Hard
1215 Stepping Numbers C++ Python O(logk + r) O(k) Medium πŸ”’ Precompute, Binary Search
1245 Tree Diameter C++ Python O(|V| + |E|) O(|E|) Medium

Depth-First Search

# Title Solution Time Space Difficulty Tag Note
0112 Path Sum Python O(n) O(h) Easy
0113 Path Sum II Python O(n) O(h) Medium
0199 Binary Tree Right Side View Python O(n) O(h) Medium
0200 Number of Islands Python O(m * n) O(m * n) Medium
0236 Lowest Common Ancestor of a Binary Tree C++ Python O(n) O(h) Medium EPI
0247 Strobogrammatic Number II C++ Python O(n^2 * 5^(n/2)) O(n) Medium πŸ”’
0250 Count Univalue Subtrees C++ Python O(n) O(h) Medium πŸ”’
0257 Binary Tree Paths C++ Python O(n * h) O(h) Easy
0282 Expression Add Operators C++ Python O(4^n) O(n) Hard
0301 Remove Invalid Parentheses C++ Python O(C(n, c)) O(c) Hard
0329 Longest Increasing Path in a Matrix C++ Python O(m * n) O(m * n) Hard
0332 Reconstruct Itinerary C++ Python O(t! / (n1! * n2! * ... nk!)) O(t) Medium
0339 Nested List Weight Sum C++ Python O(n) O(h) Easy πŸ”’
0364 Nested List Weight Sum II C++ Python O(n) O(h) Medium πŸ”’
0366 Find Leaves of Binary Tree C++ Python O(n) O(h) Medium πŸ”’
0399 Evaluate Division C++ Python O(q * |V|!) O(e) Medium
0417 Pacific Atlantic Water Flow C++ Python O(m * n) O(m * n) Medium
0440 K-th Smallest in Lexicographical Order C++ Python O(logn) O(logn) Hard
0464 Can I Win C++ Python O(n!) O(n) Medium
0515 Find Largest Value in Each Tree Row C++ Python O(n) O(h) Medium
0547 Friend Circles C++ Python O(n^2) O(n) Medium Union Find
0582 Kill Process C++ Python O(n) O(n) Medium πŸ”’ DFS, BFS
0638 Shopping Offers C++ Python O(n * 2^n) O(n) Medium
0690 Employee Importance C++ Python O(n) O(h) Easy DFS, BFS
0694 Number of Distinct Islands C++ Python O(m * n) O(m * n) Medium πŸ”’
0695 Max Area of Island C++ Python O(m * n) O(m * n) Easy
0711 Number of Distinct Islands II C++ Python O((m * n) * log(m * n)) O(m * n) Hard πŸ”’ Hash
0733 Max Area of Island C++ Python O(m * n) O(m * n) Easy
0749 Contain Virus C++ Python O((m * n)^(4/3)) O(m * n) Hard Simulation
0753 Cracking the Safe C++ Python O(k^n) O(k^n) Hard de Bruijn sequences, Lyndon word
0756 Pyramid Transition Matrix C++ Python O(a^b) O(a^b) Medium
0785 Is Graph Bipartite? C++ Python O(|V| + |E|) O(|V|) Medium
0797 All Paths From Source to Target C++ Python O(p + r * n) O(n) Medium
0802 Find Eventual Safe States C++ Python O(|V| + |E|) O(|V|) Medium
0827 Making A Large Island C++ Python O(n^2) O(n^2) Hard
0834 Sum of Distances in Tree C++ Python O(n) O(n) Hard
0841 Keys and Rooms C++ Python O(n!) O(n) Medium
0851 Loud and Rich C++ Python O(q + r) O(q + r) Medium
0913 Cat and Mouse C++ Python O(n^3) O(n^2) Hard
1020 Number of Enclaves C++ Python O(m * n) O(m * n) Medium
1059 All Paths from Source Lead to Destination C++ Python O(n + e) O(n + e) Medium πŸ”’
1192 Critical Connections in a Network C++ Python O(|V| + |E|) O(|V| + |E|) Hard Tarjan's Algorithm, Bridge Finding Algorithm
1202 Smallest String With Swaps C++ Python O(nlogn) O(n) Medium Union Find
1254 Number of Closed Islands C++ Python O(m * n) O(1) Medium

Backtracking

# Title Solution Time Space Difficulty Tag Note
0017 Letter Combinations of a Phone Number Python O(n * 4^n) O(n) Medium
0022 Generate Parentheses Python O(4^n / n^(3/2)) O(n) Medium
0037 Sudoku Solver Python O((9!)^9) O(1) Hard
0039 Combination Sum Python O(k * n^k) O(k) Medium
0040 Combination Sum II Python O(k * C(n, k)) O(k) Medium
0046 Permutations Python O(n * n!) O(n) Medium
0047 Permutations II Python O(n * n!) O(n) Medium
0051 N-Queens Python O(n!) O(n) Hard
0052 N-Queens-II Python O(n!) O(n) Hard
0077 Combinations Python O(O(k * C(n, k))) O(k) Medium
0079 Word Search Python O(m * n * l) O(l) Medium
0093 Restore IP Addresses Python O(1) O(1) Medium
0078 Subsets C++ Python O(n * 2^n) O(1) Medium
0090 Subsets II C++ Python O(n * 2^n) O(1) Medium
0126 Word Ladder II Python O(n * d) O(d) Hard
0131 Palindrome Partitioning Python O(n^2) ~ O(2^n) O(n^2) Medium
0140 Word Break II C++ Python O(n * l^2 + n * r) O(n^2) Hard
0212 Word Search II C++ Python O(m * n * l) O(l) Hard LintCode Trie, DFS
0216 Combination Sum III C++ Python O(k * C(n, k)) O(k) Medium
0254 Factor Combinations C++ Python O(nlogn) O(logn) Medium πŸ”’
0267 Palindrome Permutation II C++ Python O(n * n!) O(n) Medium πŸ”’
0291 Word Pattern II C++ Python O(n * C(n - 1, c - 1)) O(n + c) Hard πŸ”’
0294 Flip Game II C++ Python O(n + c^2) O(c) Medium πŸ”’ DP, Hash
0320 Generalized Abbreviation C++ Python O(n * 2^n) O(n) Medium πŸ”’
0425 Word Squares C++ Python O(n^2 * n!) O(n^2) Hard πŸ”’
0526 Beautiful Arrangement C++ Python O(n!) O(n) Medium
0676 Implement Magic Dictionary C++ Python O(n) O(d) Medium Trie, DFS
0679 24 Game C++ Python O(1) O(1) Hard DFS
0698 Partition to K Equal Sum Subsets C++ Python O(n * 2^n) O(2^n) Medium DFS, DP, Memoization
0718 Maximum Length of Repeated Subarray C++ Python O(m * n) O(min(m, n)) Medium DP, Hash, Binary Search
0784 Letter Case Permutation C++ Python O(n * 2^n) O(1) Easy
0996 Number of Squareful Arrays C++ Python O(n!) O(n^2) Hard
1087 Brace Expansion C++ Python O(p * l * log(p * l)) O(p * l) Medium πŸ”’
1096 Brace Expansion II C++ Python O(p * l * log(p * l)) O(p * l) Hard
1219 Path with Maximum Gold C++ Python O(m^2 * n^2) O(m * n) Medium
1240 Tiling a Rectangle with the Fewest Squares C++ Python O(n^2 * m^2 * m^(n * m)) O(n * m) Hard
1255 Maximum Score Words Formed by Letters C++ Python O(n * 2^n) O(n) Hard

Dynamic Programming

# Title Solution Time Space Difficulty Tag Note
0010 Regular Expression Matching Python O(m * n) O(n) Hard
0044 Wildcard Matching Python O(m * n) O(1) Hard Greedy
0053 Maximum Subarray C++ Python O(n) O(1) Medium
0062 Unique Paths Python O(m * n) O(m + n) Medium
0063 Unique Paths II Python O(m * n) O(m + n) Medium
0064 Minimum Path Sum Python O(m * n) O(m + n) Medium
0070 Climbing Stairs C++ Python O(logn) O(1) Easy Matrix Exponentiation
0072 Edit Distance Python O(m * n) O(m + n) Hard
0087 Scramble String Python O(n^4) O(n^3) Hard
0091 Decode Ways C++ Python O(n) O(1) Medium
0096 Unique Binary Search Trees Python O(n) O(1) Medium Math
0097 Interleaving String Python O(m * n) O(m + n) Hard
0115 Distinct Subsequences Python O(n^2) O(n) Hard
0120 Triangle Python O(m * n) O(n) Medium
0123 Best Time to Buy and Sell Stock III Python O(n) O(1) Hard
0132 Palindrome Partitioning II Python O(n^2) O(n^2) Hard
0139 Word Break C++ Python O(n * l^2) O(n) Medium
0152 Maximum Product Subarray Python O(n) O(1) Medium
0174 Dungeon Game Python O(m * n) O(m + n) Hard
0188 Best Time to Buy and Sell Stock IV Python O(k * n) O(k) Hard
0198 House Robber C++ Python O(n) O(1) Easy
0213 House Robber II C++ Python O(n) O(1) Medium
0221 Maximal Square C++ Python O(n^2) O(n) Medium EPI
0256 Paint House C++ Python O(n) O(1) Medium πŸ”’
0265 Paint House II C++ Python O(n * k) O(k) Hard πŸ”’
0276 Paint Fence C++ Python O(n) O(1) Easy πŸ”’
0279 Perfect Squares C++ Python O(n * sqrt(n)) O(n) Medium Hash
0303 Range Sum Query - Immutable C++ Python ctor: O(n), lookup: O(1) O(n) Easy
0304 Range Sum Query 2D - Immutable C++ Python ctor: O(m * n), lookup: O(1) O(m * n) Medium
0309 Best Time to Buy and Sell Stock with Cooldown C++ Python O(n) O(1) Medium
0312 Burst Balloons C++ Python O(n^3) O(n^2) Hard
0322 Coin Change C++ Python O(n * k) O(k) Medium
0351 Android Unlock Patterns C++ Python O(9^2 * 2^9) O(9 * 2^9) Medium πŸ”’ Backtracking
0357 Count Numbers with Unique Digits C++ Python O(n) O(1) Medium Backtracking, Math
0361 Bomb Enemy C++ Python O(m * n) O(m * n) Medium πŸ”’
0368 Largest Divisible Subset C++ Python O(n^2) O(n) Medium
0375 Guess Number Higher or Lower II C++ Python O(n^2) O(n^2) Medium
0377 Combination Sum IV C++ Python O(nlogn + n * t) O(t) Medium
0403 Frog Jump C++ Python O(n^2) O(n^2) Hard
0416 Partition Equal Subset Sum C++ Python O(n * s) O(s) Medium
0418 Sentence Screen Fitting C++ Python O(r + n * c) O(n) Medium πŸ”’
0446 Arithmetic Slices II - Subsequence C++ Python O(n^2) O(n * d) Hard
0465 Optimal Account Balancing C++ Python O(n * 2^n) O(2^n) Hard πŸ”’
0466 Count The Repetitions C++ Python O(s1 * min(s2, n1)) O(s2) Hard
0467 Unique Substrings in Wraparound String C++ Python O(n) O(1) Medium
0471 Encode String with Shortest Length C++ Python O(n^3) on average O(n^2) Medium πŸ”’
0472 Concatenated Words C++ Python O(n * l^2) O(n * l) Medium
0474 Ones and Zeroes C++ Python O(s * m * n) O(m * n) Medium
0486 Predict the Winner C++ Python O(n^2) O(n) Medium
0509 Fibonacci Number C++ Python O(logn) O(1) Easy variant of Climbing Stairs Matrix Exponentiation
0514 Freedom Trail C++ Python O(k) ~ O(k * r^2) O(r) Hard
0516 Longest Palindromic Subsequence C++ Python O(n^2) O(n) Medium
0546 Remove Boxes C++ Python O(n^3) ~ O(n^4) O(n^3) Hard
0552 Student Attendance Record II C++ Python O(n) O(1) Hard
0562 Longest Line of Consecutive One in Matrix C++ Python O(m * n) O(n) Medium πŸ”’
0568 Maximum Vacation Days C++ Python O(n^2 * k) O(k) Hard πŸ”’
0576 Out of Boundary Paths C++ Python O(N * m * n) O(m * n) Medium
0583 Delete Operation for Two Strings C++ Python O(m * n) O(n) Medium
0600 Non-negative Integers without Consecutive Ones C++ Python O(1) O(1) Hard
0629 K Inverse Pairs Array C++ Python O(n * k) O(k) Hard
0639 Decode Ways II C++ Python O(n) O(1) Hard
0650 2 Keys Keyboard C++ Python O(sqrt(n)) O(1) Medium
0656 Coin Path C++ Python O(n * B) O(n) Hard πŸ”’
0664 Strange Printer C++ Python O(n^3) O(n^2) Hard
0673 Number of Longest Increasing Subsequence C++ Python O(n^2) O(n) Medium
0688 Knight Probability in Chessboard C++ Python O(k * n^2) O(n^2) Medium
0689 Maximum Sum of 3 Non-Overlapping Subarrays C++ Python O(n) O(n) Hard
0691 Stickers to Spell Word C++ Python O(T * S^T) O(T * S^T) Hard Backtracking, Memoization
0712 Minimum ASCII Delete Sum for Two Strings C++ Python O(m * n) O(n) Medium
0714 Best Time to Buy and Sell Stock with Transaction Fee C++ Python O(n) O(1) Medium
0727 Minimum Window Subsequence C++ Python O(s * t) O(s) Hard πŸ”’
0730 Count Different Palindromic Subsequences C++ Python O(n^2) O(n) Hard
0740 Delete and Earn C++ Python O(n) O(1) Medium
0741 Cherry Pickup C++ Python O(n^3) O(n^2) Hard
0746 Min Cost Climbing Stairs C++ Python O(n) O(1) Easy
0750 Number Of Corner Rectangles C++ Python O(n * m^2) O(n * m) Medium
0764 Largest Plus Sign C++ Python O(n^2) O(n^2) Medium
0788 Rotated Digits C++ Python O(logn) O(logn) Easy Memoization
0790 Domino and Tromino Tiling C++ Python O(logn) O(1) Medium Matrix Exponentiation
0799 Champagne Tower C++ Python O(n^2) O(n) Medium
0801 Minimum Swaps To Make Sequences Increasing C++ Python O(n) O(1) Medium
0805 Split Array With Same Average C++ Python O(n^4) O(n^3) Hard
0808 Soup Servings C++ Python O(1) O(1) Medium Memoization
0813 Largest Sum of Averages C++ Python O(k * n^2) O(n) Medium
0818 Race Car C++ Python O(nlogn) O(n) Hard
0823 Binary Trees With Factors C++ Python O(n^2) O(n) Medium
0837 New 21 Game C++ Python O(n) O(n) Medium
0838 Push Dominoes C++ Python O(n) O(n) Medium
0847 Shortest Path Visiting All Nodes C++ Python O(n *2^n) O(n * 2^n) Hard BFS
0877 Stone Game C++ Python O(n^2) O(n) Medium variant of Predict the Winner
0879 Profitable Schemes C++ Python O(n * p * g) O(p * g) Hard
0903 Valid Permutations for DI Sequence C++ Python O(n^2) O(n) Hard
0920 Number of Music Playlists C++ Python O(n * l) O(l) Hard
0926 Flip String to Monotone Increasing C++ Python O(n) O(1) Medium
0931 Minimum Falling Path Sum C++ Python O(n^2) O(1) Medium
0935 Knight Dialer C++ Python O(logn) O(1) Medium Matrix Exponentiation
0940 Distinct Subsequences II C++ Python O(n) O(1) Hard
0943 Find the Shortest Superstring C++ Python O(n^2 * (l^2 + 2^n)) O(n^2) Hard
0956 Tallest Billboard C++ Python O(n * 3^(n/2)) O(3^(n/2)) Hard
0960 Delete Columns to Make Sorted III C++ Python O(n * l^2) O(l) Hard
0964 Least Operators to Express Number C++ Python O(logn / logx) O(logn) Hard Math
0975 Odd Even Jump C++ Python O(nlogn) O(n) Hard Mono Stack, BST
0980 Unique Paths III C++ Python O((m * n) * 2^(m * n)) O((m * n) * 2^(m * n)) Hard
0983 Minimum Cost For Tickets C++ Python O(n) O(1) Medium
1000 Minimum Cost to Merge Stones C++ Python O(n^3) O(n^3) Hard Memoization
1027 Longest Arithmetic Sequence C++ Python O(n^2) O(n^2) Medium
1035 Uncrossed Lines C++ Python O(m * n) O(min(m, n)) Medium
1039 Minimum Score Triangulation of Polygon C++ Python O(n^3) O(n^2) Medium
1043 Partition Array for Maximum Sum C++ Python O(n * k) O(k) Medium
1048 Longest String Chain C++ Python O(n * l^2) O(n * l) Medium
1049 Last Stone Weight II C++ Python O(2^n) O(2^n) Medium
1066 Campus Bikes II C++ Python O(w * b * 2^b) O(w * b * 2^b) Medium πŸ”’
1092 Shortest Common Supersequence C++ Python O(m * n) O(m * n) Hard
1105 Filling Bookcase Shelves C++ Python O(n^2) O(n) Medium
1125 Smallest Sufficient Team C++ Python O(m * 2^n) O(2^n) Hard
1137 N-th Tribonacci Number C++ Python O(logn) O(1) Easy variant of Fibonacci Number Matrix Exponentiation
1139 Largest 1-Bordered Square C++ Python O(n^3) O(n^2) Medium
1140 Stone Game II C++ Python O(n*(logn)^2) O(nlogn) Medium
1143 Longest Common Subsequence C++ Python O(m * n) O(min(m, n)) Medium
1155 Number of Dice Rolls With Target Sum C++ Python O(d * f * t) O(t) Medium
1182 Shortest Distance to Target Color C++ Python O(n) O(n) Medium πŸ”’
1186 Maximum Subarray Sum with One Deletion C++ Python O(n) O(1) Medium
1187 Make Array Strictly Increasing C++ Python O(n^2 * logn) O(n) Hard
1191 K-Concatenation Maximum Sum C++ Python O(n) O(1) Medium
1216 Valid Palindrome III C++ Python O(n^2) O(n) Hard πŸ”’, variant of Longest Palindromic Subsequence
1218 Longest Arithmetic Subsequence of Given Difference C++ Python O(n) O(n) Medium
1220 Count Vowels Permutation C++ Python O(logn) O(1) Hard Matrix Exponentiation
1223 Dice Roll Simulation C++ Python O(m * n) O(m) Medium
1230 Toss Strange Coins C++ Python O(n^2) O(n) Medium
1235 Maximum Profit in Job Scheduling C++ Python O(nlogn) O(n) Hard DP, Heap
1239 Maximum Length of a Concatenated String with Unique Characters C++ Python O(n) ~ O(2^n) O(1) ~ O(2^n) Medium DP, Bit Manipulation
1246 Palindrome Removal C++ Python O(n^3) O(n^2) Hard

Greedy

# Title Solution Time Space Difficulty Tag Note
0011 Container With Most Water C++ Python O(n) O(1) Medium
0042 Trapping Rain Water C++ Python O(n) O(1) Hard Tricky
0045 Jump Game II Python O(n) O(1) Hard
0055 Jump Game Python O(n) O(1) Medium
0122 Best Time to Buy and Sell Stock II C++ Python O(n) O(1) Easy
0134 Gas Station Python O(n) O(1) Medium
0135 Candy C++ Python O(n) O(n) Hard
0316 Remove Duplicate Letters C++ Python O(n) O(1) Hard Mono Stack
0321 Create Maximum Number C++ Python O(k * (m + n + k)) ~ O(k * (m + n + k^2)) O(m + n + k^2) Hard variant of Delete Digits Greedy, DP
0330 Patching Array C++ Python O(s + logn) O(1) Hard
0376 Wiggle Subsequence C++ Python O(n) O(1) Medium
0392 Is Subsequence C++ Python O(n) O(1) Medium
0397 Integer Replacement C++ Python O(n) O(1) Medium Math
0402 Remove K Digits C++ Python O(n) O(n) Medium LintCode
0435 Non-overlapping Intervals C++ Python O(nlogn) O(1) Medium Line Sweep
0452 Minimum Number of Arrows to Burst Balloons C++ Python O(nlogn) O(1) Medium
0455 Assign Cookies C++ Python O(nlogn) O(1) Easy
0621 Task Scheduler C++ Python O(n) O(1) Medium
0630 Course Schedule III C++ Python O(nlogn) O(k) Hard
0646 Maximum Length of Pair Chain C++ Python O(nlogn) O(1) Medium variant of Non-overlapping Intervals Line Sweep
0649 Dota2 Senate C++ Python O(n) O(n) Medium
0659 Split Array into Consecutive Subsequences C++ Python O(n) O(1) Medium
0738 Monotone Increasing Digits C++ Python O(1) O(1) Medium
0757 Set Intersection Size At Least Two C++ Python O(nlogn) O(n) Hard
0759 Employee Free Time C++ Python O(m * logn) O(n) Hard
0763 Partition Labels C++ Python O(n) O(n) Medium
0767 Reorganize String C++ Python O(n) O(1) Medium
0798 Smallest Rotation with Highest Score C++ Python O(n) O(1) Hard
0843 Guess the Word C++ Python O(n^2) O(n) Hard MinMax
0861 Score After Flipping Matrix C++ Python O(r * c) O(1) Medium
0870 Advantage Shuffle C++ Python O(nlogn) O(n) Medium
0881 Boats to Save People C++ Python O(nlogn) O(n) Medium
0936 Stamping The Sequence C++ Python O((n - m) * m) O((n - m) * m) Hard
0948 Bag of Tokens C++ Python O(nlogn) O(1) Medium Two Pointers
0962 Maximum Width Ramp C++ Python O(n) O(n) Medium Mono Stack
0968 Binary Tree Cameras C++ Python O(n) O(h) Hard DFS
0984 String Without AAA or BBB C++ Python O(a + b) O(1) Easy
0991 Broken Calculator C++ Python O(logn) O(1) Medium
0995 Minimum Number of K Consecutive Bit Flips C++ Python O(n) O(1) Hard
1005 Maximize Sum Of Array After K Negations C++ Python O(n) on average O(1) Easy Quick Select
1024 Video Stitching C++ Python O(nlogn) O(1) Medium variant of Jump Game II
1029 Two City Scheduling C++ Python O(n) on average O(1) Easy Quick Select
1053 Previous Permutation With One Swap C++ Python O(n) O(1) Medium
1055 Shortest Way to Form String C++ Python O(m + n) O(m) Medium πŸ”’, variant of Minimum Window Subsequence
1058 Minimize Rounding Error to Meet Target C++ Python O(n) on average O(n) Medium πŸ”’ Quick Select
1081 Smallest Subsequence of Distinct Characters C++ Python O(n) O(1) Medium same as Remove Duplicate Letters Mono Stack
1090 Largest Values From Labels C++ Python O(nlogn) O(n) Medium
1111 Maximum Nesting Depth of Two Valid Parentheses Strings C++ Python O(n) O(1) Medium
1167 Minimum Cost to Connect Sticks C++ Python O(nlogn) O(n) Medium πŸ”’
1183 Maximum Number of Ones C++ Python O(1) O(1) Hard πŸ”’
1196 How Many Apples Can You Put into the Basket C++ Python O(nlogn) O(n) Easy πŸ”’
1199 Minimum Time to Build Blocks C++ Python O(nlogn) O(n) Hard πŸ”’
1221 Split a String in Balanced Strings C++ Python O(n) O(1) Easy
1247 Minimum Swaps to Make Strings Equal C++ Python O(n) O(1) Easy
1249 Minimum Remove to Make Valid Parentheses C++ Python O(n) O(1) Medium Stack
1253 Reconstruct a 2-Row Binary Matrix C++ Python O(n) O(1) Medium

Graph

# Title Solution Time Space Difficulty Tag Note
0765 Couples Holding Hands C++ Python O(n) O(n) Hard
0924 Minimize Malware Spread C++ Python O(n^2) O(n) Hard Union Find
0928 Minimize Malware Spread II C++ Python O(n^2) O(n) Hard Union Find
0959 Regions Cut By Slashes C++ Python O(n^2) O(n^2) Medium Union Find
0990 Satisfiability of Equality Equations C++ Python O(n) O(1) Medium Union Find
1042 Flower Planting With No Adjacent C++ Python O(n) O(n) Easy
1101 The Earliest Moment When Everyone Become Friends C++ Python O(nlogn) O(n) Medium πŸ”’ Union Find
1135 Connecting Cities With Minimum Cost C++ Python O(nlogn) O(n) Medium πŸ”’ Union Find, Kruskal's Algorithm, MST
1168 Optimize Water Distribution in a Village C++ Python O(nlogn) O(n) Hard πŸ”’ Union Find

Geometry

# Title Solution Time Space Difficulty Tag Note
0587 Erect the Fence C++ Python O(nlogn) O(n) Hard Convex Hull, Monotone Chain
0892 Surface Area of 3D Shapes C++ Python O(n^2) O(1) Easy

Simulation

# Title Solution Time Space Difficulty Tag Note
0874 Walking Robot Simulation C++ Python O(n + k) O(k) Easy
1138 Alphabet Board Path C++ Python O(n) O(1) Medium
1243 Array Transformation C++ Python O(n^2) O(n) Easy

Design

# Title Solution Time Space Difficulty Tag Note
0146 LRU Cache C++ Python O(1) O(k) Hard
0225 Implement Stack using Queues C++ Python push: O(n), pop: O(1), top: O(1) O(n) Easy
0284 Peeking Iterator C++ Python O(1) O(1) Medium
0348 Design Tic-Tac-Toe C++ Python O(1) O(n^2) Medium πŸ”’
0353 Design Snake Game C++ Python O(1) O(s) Medium πŸ”’ Deque
0355 Design Twitter C++ Python O(klogu) O(t + f) Medium LintCode Heap
0359 Logger Rate Limiter C++ Python O(1), amortized O(k) Easy πŸ”’ Deque
0362 Design Hit Counter C++ Python O(1), amortized O(k) Medium πŸ”’ Deque
0379 Design Phone Directory C++ Python O(1) O(n) Medium πŸ”’
0380 Insert Delete GetRandom O(1) C++ Python O(1) O(n) Hard
0381 Insert Delete GetRandom O(1) - Duplicates allowed C++ Python O(1) O(n) Hard
0432 All O`one Data Structure C++ Python O(1) O(n) Hard
0460 LFU Cache C++ Python O(1) O(k) Hard
0535 Encode and Decode TinyURL C++ Python O(1) O(n) Medium
0588 Design In-Memory File System C++ Python ls: O(l + klogk)
mkdir: O(l)
addContentToFile: O(l + c)
readContentFromFile: O(l + c)
O(n + s) Hard πŸ”’
0604 Design Compressed String Iterator C++ Python O(1) O(1) Easy πŸ”’
0631 Design Excel Sum Formula C++ Python set: O((r * c)^2)
get: O(1)
sum: O((r * c)^2)
O(r * c) Hard πŸ”’
0635 Design Log Storage System C++ Python put: O(1)
retrieve: O(n + dlogd)
O(n) Medium πŸ”’
0642 Design Search Autocomplete System C++ Python O(p^2) O(p * t + s) Hard πŸ”’
0715 Range Module C++ Python add: O(n)
remove: O(n)
query: O(logn)
O(n) Hard
0716 Max Stack C++ Python push: O(logn)
pop: O(logn)
popMax: O(logn)
top: O(1)
peekMax: O(1)
O(n) Easy
0745 Prefix and Suffix Search C++ Python ctor: O(w * l^2)
search : O(p + s)
O(t) Hard Trie
0900 RLE Iterator C++ Python O(n) O(1) Medium
1146 Snapshot Array C++ Python set: O(1)
get: O(logn)
O(n) Medium
1166 Design File System C++ Python create: O(n)
get: O(n)
O(n) Medium πŸ”’
1172 Dinner Plate Stacks C++ Python push: O(logn)
pop: O(1), amortized
popAtStack: (logn)
O(n * c) Hard
1206 Design Skiplist C++ Python O(logn), on average O(n) Hard
1236 Web Crawler C++ Python O(|V| + |E|) O(|V|) Medium πŸ”’
1244 Design A Leaderboard C++ Python ctor: O(1)
add: O(1)
top: O(n)
reset: O(1)
O(n) Medium

Concurrency

# Title Solution Time Space Difficulty Tag Note
1114 Print in Order C++ Python O(n) O(1) Easy
1115 Print FooBar Alternately C++ Python O(n) O(1) Medium
1116 Print Zero Even Odd C++ Python O(n) O(1) Medium
1117 Building H2O C++ Python O(n) O(1) Hard
1188 Design Bounded Blocking Queue C++ Python O(n) O(1) Medium πŸ”’
1195 Fizz Buzz Multithreaded C++ Python O(n) O(1) Medium
1226 The Dining Philosophers C++ Python O(n) O(1) Medium
1242 Web Crawler Multithreaded C++ Python O(|V| + |E|) O(|V|) Medium πŸ”’

SQL

# Title Solution Time Space Difficulty Tag Note
0175 Combine Two Tables MySQL O(m + n) O(m + n) Easy
0176 Second Highest Salary MySQL O(n) O(1) Easy
0177 Nth Highest Salary MySQL O(n^2) O(n) Medium
0178 Rank Scores MySQL O(n^2) O(n) Medium
0180 Consecutive Numbers MySQL O(n) O(n) Medium
0181 Employees Earning More Than Their Managers MySQL O(n^2) O(1) Easy
0182 Duplicate Emails MySQL O(n^2) O(n) Easy
0183 Customers Who Never Order MySQL O(n^2) O(1) Easy
0184 Department Highest Salary MySQL O(n^2) O(n) Medium
0185 Department Top Three Salaries MySQL O(n^2) O(n) Hard
0196 Delete Duplicate Emails MySQL O(n^2) O(n) Easy
0197 Rising Temperature MySQL O(n^2) O(n) Easy
0262 Trips and Users MySQL O((t * u) + tlogt) O(t) Hard
0511 Game Play Analysis I MySQL O(n) O(n) Easy πŸ”’
0512 Game Play Analysis II MySQL O(n) O(n) Easy πŸ”’
0534 Game Play Analysis III MySQL O(nlogn) O(n) Medium πŸ”’
0550 Game Play Analysis IV MySQL O(n) O(n) Medium πŸ”’
1045 Customers Who Bought All Products MySQL O(n + k) O(n + k) Medium πŸ”’
1050 Actors and Directors Who Cooperated At Least Three Times MySQL O(n) O(n) Easy πŸ”’
1068 Product Sales Analysis I MySQL O(m + n) O(m + n) Easy πŸ”’
1069 Product Sales Analysis II MySQL O(n) O(n) Easy πŸ”’
1070 Product Sales Analysis III MySQL O(n) O(n) Medium πŸ”’
1075 Project Employees I MySQL O(m + n) O(m + n) Easy πŸ”’
1076 Project Employees II MySQL O(n) O(n) Easy πŸ”’
1077 Project Employees III MySQL O((m + n)^2) O(m + n) Medium πŸ”’
1082 Sales Analysis I MySQL O(n) O(n) Easy πŸ”’
1083 Sales Analysis II MySQL O(m + n) O(m + n) Easy πŸ”’
1084 Sales Analysis III MySQL O(m + n) O(m + n) Easy πŸ”’
1097 Game Play Analysis V MySQL O(n^2) O(n) Hard πŸ”’
1098 Unpopular Books MySQL O(m + n) O(n) Medium πŸ”’
1107 New Users Daily Count MySQL O(n) O(n) Medium πŸ”’
1112 Highest Grade For Each Student MySQL O(nlogn) O(n) Medium πŸ”’
1113 Reported Posts MySQL O(n) O(n) Easy πŸ”’
1126 Active Businesses MySQL O(n) O(n) Medium πŸ”’
1127 User Purchase Platform MySQL O(n) O(n) Hard πŸ”’
1132 Reported Posts II MySQL O(m + n) O(n) Medium πŸ”’
1141 User Activity for the Past 30 Days I MySQL O(n) O(n) Easy πŸ”’
1142 User Activity for the Past 30 Days II MySQL O(n) O(n) Easy πŸ”’
1148 Article Views I MySQL O(nlogn) O(n) Easy πŸ”’
1149 Article Views II MySQL O(nlogn) O(n) Medium πŸ”’
1158 Market Analysis I MySQL O(m + n) O(m + n) Medium πŸ”’
1159 Market Analysis II MySQL O(m + n) O(m + n) Hard πŸ”’
1164 Product Price at a Given Date MySQL O(mlogn) O(m) Medium πŸ”’
1173 Immediate Food Delivery I MySQL O(n) O(1) Easy πŸ”’
1174 Immediate Food Delivery II MySQL O(n) O(m) Medium πŸ”’
1179 Reformat Department Table MySQL O(n) O(n) Easy πŸ”’
1193 Monthly Transactions I MySQL O(n) O(n) Medium πŸ”’
1194 Tournament Winners MySQL O(m + n + nlogn) O(m + n) Hard πŸ”’
1204 Last Person to Fit in the Elevator MySQL O(nlogn) O(n) Medium πŸ”’
1205 Monthly Transactions II MySQL O(n) O(n) Medium πŸ”’
1211 Queries Quality and Percentage MySQL O(n) O(n) Easy
1212 Team Scores in Football Tournament MySQL O(nlogn) O(n) Medium
1225 Report Contiguous Dates MySQL O(nlogn) O(n) Hard πŸ”’
1241 Number of Comments per Post MySQL O(n) O(n) Easy πŸ”’
1251 Average Selling Price MySQL O(n) O(n) Easy πŸ”’

Shell Script

# Title Solution Time Space Difficulty Tag Note
0192 Word Frequency Shell O(n) O(k) Medium
0193 Valid Phone Numbers Shell O(n) O(1) Easy
0194 Transpose File Shell O(n^2) O(n^2) Medium
0195 Tenth Line Shell O(n) O(1) Easy

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