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Remove Element
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Remove Element
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/*
LeetCode 27:
Given an array and a value, remove all instances of that value in-place and return the new length.
Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.
The order of elements can be changed. It doesn't matter what you leave beyond the new length.
Example:
Given nums = [3,2,2,3], val = 3,
Your function should return length = 2, with the first two elements of nums being 2.
Solution:
Language: C++
Tag: 2Pointer
*/
class Solution {
public:
int removeElement(vector<int>& nums, int val) {
/*
// 1. two pointers -- O(n) time + O(1) space
int idx = 0;
for (int i = 0; i < nums.size(); ++i) {
if (nums[i] != val) {
nums[idx++] = nums[i];
}
}
return idx;
*/
// 2. two pointers -- O(n) time + O(1) space <better -- minimum swap operations>
int left = 0, right = nums.size() - 1;
while (left <= right) {
if (nums[left] != val) {
++left;
} else {
nums[left] = nums[right--];
}
}
return left;
}
};