leetcode-73 set matrix zeros

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

题意是将矩阵中，有0的行列值均置为0.

这道题想要原址，首先需要记录下首行、首列，是否有0。其次从2行2列开始统计，如果有0，则将此位置的首行、首列位置记为0，实现原址。

在改的时候应当注意，首行首列的值需要最后更改。

感谢博主  http://blog.csdn.net/ljiabin/article/details/40423045

附上代码

class Solution {public:void setZeroes(vector<vector<int>>& matrix){if (matrix.empty())return;int row = matrix.size();int col = matrix[0].size();bool firstrow_has_zero = false;bool firstcol_has_zero = false;//判断首行首列有没有0for (int j = 0; j < col; j++){if (matrix[0][j] == 0){firstrow_has_zero = true;break;}}for (int i = 0; i < row; i++){if (matrix[i][0] == 0){firstcol_has_zero = true;break;}}//从2行2列开始标记，是否有0for (int i = 1; i<row; i++){for (int j = 1; j<col; j++){if (matrix[i][j] == 0){matrix[0][j] = 0;matrix[i][0] = 0;}}}//第一列为0的判断for (int i = 1; i<row; i++){if (matrix[i][0] == 0){for (int j = 1; j<col; j++){matrix[i][j] = 0;}}}//第一行为0的判断for (int j = 1; j<col; j++){if (matrix[0][j] == 0){for (int i = 1; i<row; i++){matrix[i][j] = 0;}}}if (firstcol_has_zero){for (int i = 0; i < row; i++){matrix[i][0] = 0;}}if (firstrow_has_zero){for (int j = 0; j < col; j++){matrix[0][j] = 0;}}return;}};