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by Sumit Chourasia | Oct 31, 2020 | Category :coding | Tags : algorithm array data-structure leetcode medium

Set Matrix Zeroes - Array - Medium - LeetCode

Set Matrix Zeroes - Array - Medium - LeetCode

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

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?
 

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
-231 <= matrix[i][j] <= 231 - 1

public class Solution {
    public void SetZeroes(int[][] matrix) {
        var setRow = new HashSet<int>();
        var setCol = new HashSet<int>();
        
        for(int i=0;i<matrix.Length;i++){
            for(int j=0;j<matrix[0].Length;j++){
                if(matrix[i][j]==0){
                    setRow.Add(i);
                    setCol.Add(j);
                }
            }
        }
        
        for(int i=0;i<matrix.Length;i++){
            for(int j=0;j<matrix[0].Length;j++){
                if(setRow.Contains(i) || setCol.Contains(j)){
                    matrix[i][j]=0;
                }
            }
        }
                
    }
}

Time Complexity: O(n^2)

Space Complexity: O(n)