LeetCode-Set Matrix Zeroes

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?

解题思路：没想到好的方法，就是最简单的O(m*n）。就是搜到一个0，就把行列都变为0，用了一个符号数组，识别是以前的0，还是变成的0.

class Solution {
public:
    void setZeroes(vector<vector<int> > &matrix) {
    size_t m = matrix.size();
    size_t n = matrix[0].size();
    int s[m][n];
    for(size_t i = 0 ;i != m;i++)
      for(size_t j = 0 ;j !=n;j++)
        s[i][j] = 1;

    for(size_t i = 0 ;i != m;i++)
      for(size_t j = 0 ;j !=n;j++) {
        if(matrix[i][j] == 0 && s[i][j] != -1) {
         for(size_t k = 0; k != n;k++) {
          if(matrix[i][k]!=0 )
            s[i][k] = -1;
          matrix[i][k] = 0;
         }
         for(size_t l = 0; l != m;l++) {
        if(matrix[l][j]!=0 )
            s[l][j] = -1;
           matrix[l][j] = 0;
         }
          
        }
      }
    }
};