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.

click to show follow up.

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?

体比较常见，但是如何用最少的内存呢？

记录出现0的位置要用0个数个空间，不是常数。

在0排和0列记录哪排哪列需要置零。这两行需要在修改之前判断是否需要置零，只需2个额外空间。

class Solution {
public:
    void setZeroes(vector<vector<int> > &matrix) {
        int flag1 = 0;
        int flag0 = 0;
        
        for(int i = 0 ; i < matrix.size();i++)
        if(matrix[i][0] == 0)flag1 = 1;
        
        for(int i = 0 ; i < matrix[0].size();i++)
        if(matrix[0][i] == 0)flag0 = 1;
        
        for(int i = 1 ; i < matrix.size();i++)
        for(int j = 1 ; j < matrix[0].size();j++)
        {
            if(matrix[i][j] == 0)
            {
                matrix[0][j] = 0;
                matrix[i][0] = 0;
            }
        }
        
        for(int i = 1 ; i < matrix.size();i++)
        {
            if(matrix[i][0] == 0)
            for(int j = 1 ; j < matrix[i].size();j++)matrix[i][j]=0;
        }
        for(int i = 1 ; i < matrix[0].size();i++)
        {
            if(matrix[0][i] == 0)
            for(int j = 1 ; j < matrix.size();j++)matrix[j][i]=0;
        }
        if(flag1 == 1)for(int i = 0 ; i < matrix.size();i++)matrix[i][0] = 0;
        if(flag0 == 1)for(int i = 0 ; i < matrix[0].size();i++)matrix[0][i] = 0;
        
    }
};