[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;
        }
    }
    }