73. Set Matrix Zeroes

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

Rust Solution

struct Solution;
use std::collections::HashSet;

impl Solution {
    fn set_zeroes(matrix: &mut Vec<Vec<i32>>) {
        let mut row: HashSet<usize> = HashSet::new();
        let mut col: HashSet<usize> = HashSet::new();
        let n = matrix.len();
        let m = matrix[0].len();
        for i in 0..n {
            for j in 0..m {
                if matrix[i][j] == 0 {
                    row.insert(i);
                    col.insert(j);
                }
            }
        }
        for i in 0..n {
            for j in 0..m {
                if row.contains(&i) || col.contains(&j) {
                    matrix[i][j] = 0;
                }
            }
        }
    }
}

#[test]
fn test() {
    let mut matrix: Vec<Vec<i32>> = vec_vec_i32![[1, 1, 1], [1, 0, 1], [1, 1, 1]];
    let res: Vec<Vec<i32>> = vec_vec_i32![[1, 0, 1], [0, 0, 0], [1, 0, 1]];
    Solution::set_zeroes(&mut matrix);
    assert_eq!(matrix, res);
    let mut matrix: Vec<Vec<i32>> = vec_vec_i32![[0, 1, 2, 0], [3, 4, 5, 2], [1, 3, 1, 5]];
    let res: Vec<Vec<i32>> = vec_vec_i32![[0, 0, 0, 0], [0, 4, 5, 0], [0, 3, 1, 0]];
    Solution::set_zeroes(&mut matrix);
    assert_eq!(matrix, res);
}

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