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LeetCode

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Problem

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in-place.

Example 1:

Input:
[
  [1,1,1],
  [1,0,1],
  [1,1,1]
]
Output:
[
  [1,0,1],
  [0,0,0],
  [1,0,1]
]

Example 2:

Input:
[
  [0,1,2,0],
  [3,4,5,2],
  [1,3,1,5]
]
Output:
[
  [0,0,0,0],
  [0,4,5,0],
  [0,3,1,0]
]

Follow up:

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?

Code

class Solution {
    public void setZeroes(int[][] matrix) {
        boolean rowZero = false;
        boolean colZero = false;

        int m = matrix.length;
        int n = matrix[0].length;

        for(int i = 0; i < m; i++){
            for(int j = 0; j < n; j++){
                if(matrix[i][j] == 0){
                    if(i == 0) rowZero = true;
                    if(j == 0) colZero = true;

                    matrix[i][0] = 0;
                    matrix[0][j] = 0;
                }
            }
        }

        for(int j = 1; j < n; j++){
            if(matrix[0][j] == 0){
                for(int i = 1; i < m; i++){
                    matrix[i][j] = 0;
                }
            }
        }

        for(int i = 1; i < m; i++){
            if(matrix[i][0] == 0){
                for(int j = 0; j < n; j++){
                    matrix[i][j] = 0;
                }
            }
        }


        if(rowZero){
            for(int j = 0; j < n; j++){
                matrix[0][j] = 0;
            }
        }

        if(colZero){
            for(int i = 0; i < m; i++){
                matrix[i][0] = 0;
            }
        }
    }
}