[LeetCode97]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?

Analysis:

The solution using O(mn) space is easy, create another flag matrix for each position.

The solution using O(m+n), create two arrays to store specific row and column zero info.

The solution using constant space need us to multiplex use the matrix itself. 

Steps:

1. Determine the first row and column is 0 or not.

2.  Use matrix first row and column to store 0 information

3. Set matrix 0 according to the first row and column

4. Set first row and column to 0, according to step 1.

Java

public void setZeroes(int[][] matrix) {        // IMPORTANT: Please reset any member data you declared, as        // the same Solution instance will be reused for each test case.        boolean firstRow = false, firstColumn = false;        for(int i=0; i<matrix.length; i++){        if(matrix[i][0] == 0){        firstColumn = true;        break;        }        }                for(int i=0; i<matrix[0].length;i++){        if(matrix[0][i] == 0){        firstRow = true;        break;        }        }                for(int i=1; i<matrix.length;i++){        for(int j=1; j<matrix[0].length;j++){        if(matrix[i][j] == 0){        matrix[i][0] = 0;        matrix[0][j] = 0;        }        }        }                for(int i=1; i<matrix.length;i++){        for(int j=1; j<matrix[0].length;j++){        if(matrix[i][0] == 0 || matrix[0][j]==0){        matrix[i][j] = 0;        }        }        }                if(firstColumn){        for(int i=0; i<matrix.length;i++)        matrix[i][0] =0;        }                if(firstRow){        for(int i=0; i<matrix[0].length;i++)        matrix[0][i] =0;        }    }

c++

void setZeroes(vector<vector<int> > &matrix) {        assert(matrix.size() >0);    int row = matrix.size();    int column = matrix[0].size();    bool zeroRow = false, zeroCol = false;    for(int i=0; i<column; i++){        if(matrix[0][i] == 0)            zeroRow = true;    }    for(int i=0; i<row; i++){        if(matrix[i][0] == 0)            zeroCol = true;    }    for(int i=1; i<row; i++){        for(int j=1; j<column; j++){            if(matrix[i][j]==0){                matrix[i][0] = 0;                matrix[0][j] = 0;            }        }    }    for(int i=1; i<row; i++){        for(int j=1; j<column; j++){            if(matrix[i][0]==0 || matrix[0][j]==0)                matrix[i][j] = 0;        }    }    if(zeroRow == true){        for(int i=0; i<column;i++){            matrix[0][i] = 0;        }    }    if(zeroCol == true){        for(int i=0; i<row;i++){            matrix[i][0] = 0;        }    }    }