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36.valid-sudoku.cpp
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36.valid-sudoku.cpp
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/*
* @lc app=leetcode id=36 lang=cpp
*
* [36] Valid Sudoku
*
* https://leetcode.com/problems/valid-sudoku/description/
*
* algorithms
* Medium (48.03%)
* Total Accepted: 382K
* Total Submissions: 780.9K
* Testcase Example: '[["5","3",".",".","7",".",".",".","."],["6",".",".","1","9","5",".",".","."],[".","9","8",".",".",".",".","6","."],["8",".",".",".","6",".",".",".","3"],["4",".",".","8",".","3",".",".","1"],["7",".",".",".","2",".",".",".","6"],[".","6",".",".",".",".","2","8","."],[".",".",".","4","1","9",".",".","5"],[".",".",".",".","8",".",".","7","9"]]'
*
* Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be
* validated according to the following rules:
*
*
* Each row must contain the digits 1-9 without repetition.
* Each column must contain the digits 1-9 without repetition.
* Each of the 9 3x3 sub-boxes of the grid must contain the digits 1-9 without
* repetition.
*
*
*
* A partially filled sudoku which is valid.
*
* The Sudoku board could be partially filled, where empty cells are filled
* with the character '.'.
*
* Example 1:
*
*
* Input:
* [
* ["5","3",".",".","7",".",".",".","."],
* ["6",".",".","1","9","5",".",".","."],
* [".","9","8",".",".",".",".","6","."],
* ["8",".",".",".","6",".",".",".","3"],
* ["4",".",".","8",".","3",".",".","1"],
* ["7",".",".",".","2",".",".",".","6"],
* [".","6",".",".",".",".","2","8","."],
* [".",".",".","4","1","9",".",".","5"],
* [".",".",".",".","8",".",".","7","9"]
* ]
* Output: true
*
*
* Example 2:
*
*
* Input:
* [
* ["8","3",".",".","7",".",".",".","."],
* ["6",".",".","1","9","5",".",".","."],
* [".","9","8",".",".",".",".","6","."],
* ["8",".",".",".","6",".",".",".","3"],
* ["4",".",".","8",".","3",".",".","1"],
* ["7",".",".",".","2",".",".",".","6"],
* [".","6",".",".",".",".","2","8","."],
* [".",".",".","4","1","9",".",".","5"],
* [".",".",".",".","8",".",".","7","9"]
* ]
* Output: false
* Explanation: Same as Example 1, except with the 5 in the top left corner
* being
* modified to 8. Since there are two 8's in the top left 3x3 sub-box, it
* is invalid.
*
*
* Note:
*
*
* A Sudoku board (partially filled) could be valid but is not necessarily
* solvable.
* Only the filled cells need to be validated according to the mentioned
* rules.
* The given board contain only digits 1-9 and the character '.'.
* The given board size is always 9x9.
*
*
*/
class Solution {
public:
bool isValidSudoku(vector<vector<char>>& board) {
int row[9][9] = {0};
int column[9][9] = {0};
int block[9][9] = {0};
for(auto i = 0; i < board.size(); ++i){
for (auto j = 0; j < board[0].size(); ++j){
if (board[i][j] == '.'){
continue;
}
int num = board[i][j] - '0' - 1;
int kth = i / 3 * 3 + j / 3;
if (row[i][num] || column[j][num] || block[kth][num]){
return false;
}
row[i][num] = column[j][num] = block[kth][num] = 1;
}
}
return true;
}
};