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?

不占用多余的空间，首先确定第一行及第一列是否需要置0，再通过Matrix的第一行第一列记录该行或该列是否置0

创建两个布尔型变量来标记第一行及第一列是否需要置0

public class Solution {    public void setZeroes(int[][] matrix) {        int row = matrix.length;if (row == 0)return;boolean r=false,c=false;int col = matrix[0].length;for (int i = 0; i < row; i++)  //第一行if (matrix[i][0] == 0) r=true;for (int j = 0; j < col; j++)  //第一列if (matrix[0][j] == 0) c=true;for (int i = 1; i < row; i++) {for (int j = 1; j < col; j++) {if (matrix[i][j] == 0) {matrix[i][0] = 0;matrix[0][j] = 0;}}}for (int j = 1; j < col; j++) {if (matrix[0][j] == 0)for (int i = 1; i < row; i++) {matrix[i][j] = 0;}}for (int i = 1; i < row; i++) {if (matrix[i][0] == 0)for (int j = 1; j < col; j++) {matrix[i][j] = 0;}}if (r) {  //对第一行置0for (int j = 0; j < row; j++)matrix[j][0] = 0;} if(c){   //对第一列置0for (int i = 0; i < col; i++)matrix[0][i] = 0;}    }}