73. Set Matrix Zeroes

Medium

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Given an m x n integer matrix matrix, if an element is 0, set its entire row and column to 0's.

You must do it in place.

Example 1:

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

Example 2:

Input: matrix = [[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]]

Constraints:

• m == matrix.length

• n == matrix[0].length

• 1 <= m, n <= 200

• -2<sup>31</sup> <= matrix[i][j] <= 2<sup>31</sup> - 1

Follow up:

• A straightforward 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?

Solution:

class Solution {
    public void setZeroes(int[][] matrix) {
        int n = matrix.length;
        int m = matrix[0].length;
        int[] row = new int[n];
        int[] col = new int[m];
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(matrix[i][j] == 0) {
                    row[i] = 1;
                    col[j] = 1;
                }
            }
        }
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(row[i]== 1 || col[j] == 1) {
                    matrix[i][j] = 0;
                }
            }
        }
    }
}