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;

}

};

 

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