LeetCode Set Matrix Zeroes

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.

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Follow up:

Did you use extra space?
A straight forward solution using O(mn) space is probably a bad idea.
A simple improvement uses O(m + n) space, but still not the best solution.
Could you devise a constant space solution?

题意：将0的行列置0.

思路：为了不开额外的空间，我们借助第一行和第一列，然后判断是否第一行、列也要置0

class Solution {public: void setZeroes(vector<vector<int> > &matrix) {int n = matrix.size();int m = matrix[0].size();bool firstRow = false, firstCol = false;for (int i = 0; i < n; i++) if (matrix[i][0] == 0) {firstCol = true;break;}for (int i = 0; i < m; i++) if (matrix[0][i] == 0) {firstRow = true;break;}for (int i = 1; i < n; i++) {for (int j = 1; j < m; j++) {if (matrix[i][j] == 0) {matrix[i][0] = 0;matrix[0][j] = 0;}}}for (int i = 1; i < n; i++) {if (matrix[i][0] == 0)for (int j = 1; j < m; j++)matrix[i][j] = 0;}for (int i = 1; i < m; i++) {if (matrix[0][i] == 0)for (int j = 1; j < n; j++)matrix[j][i] = 0;}if (firstRow) {for (int i = 0; i < m; i++)matrix[0][i] = 0;}if (firstCol) {for (int i = 0; i < n; i++)matrix[i][0] = 0;}}};