leetcode[73]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?

class Solution {
public:
void setZeroes(vector<vector<int> > &matrix) 
{
    if(matrix.empty())return;
    int row=matrix.size();
    if(matrix[0].empty())return;
    int col=matrix[0].size();
    int flagRow0=0,flagCol0=0;
    for(int j=0;j<col;j++)
    {
        if(matrix[0][j]==0)flagRow0=1;
    }
    for(int i=0;i<row;i++)
    {
        if(matrix[i][0]==0)flagCol0=1;
    }
    for (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;
            }
        }
    }
    for (int i=1;i<row;i++)
    {
        if(matrix[i][0]==0)
        {
            for (int j=1;j<col;j++)
            {
                matrix[i][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;
            }            
        }
    }
    if(flagRow0==1)
    {
        for(int j=0;j<col;j++)matrix[0][j]=0;
    }
    if(flagCol0==1)
    {
        for(int i=0;i<row;i++)matrix[i][0]=0;
    }
    return;
}
};