73. 矩阵置零

给定一个 m x n 的矩阵，如果一个元素为 0，则将其所在行和列的所有元素都设为 0。请使用原地算法。

示例 1:

输入: 
[
  [1,1,1],
  [1,0,1],
  [1,1,1]
]
输出: 
[
  [1,0,1],
  [0,0,0],
  [1,0,1]
]

示例 2:

输入: 
[
  [0,1,2,0],
  [3,4,5,2],
  [1,3,1,5]
]
输出: 
[
  [0,0,0,0],
  [0,4,5,0],
  [0,3,1,0]
]

代码

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