README.md

1380. Lucky Numbers in a Matrix

Given a m * n matrix of distinct numbers, return all lucky numbers in the matrix in any order.

A lucky number is an element of the matrix such that it is the minimum element in its row and maximum in its column.

Example 1:

Input: matrix = [[3,7,8],[9,11,13],[15,16,17]]
Output: [15]
Explanation: 15 is the only lucky number since it is the minimum in its row and the maximum in its column

Example 2:

Input: matrix = [[1,10,4,2],[9,3,8,7],[15,16,17,12]]
Output: [12]
Explanation: 12 is the only lucky number since it is the minimum in its row and the maximum in its column.

Example 3:

Input: matrix = [[7,8],[1,2]]
Output: [7]

Constraints:

• m == mat.length
• n == mat[i].length
• 1 <= n, m <= 50
• 1 <= matrix[i][j] <= 10^5.
• All elements in the matrix are distinct.

Solutions (Rust)

1. Solution

impl Solution {
    pub fn lucky_numbers (matrix: Vec<Vec<i32>>) -> Vec<i32> {
        let m = matrix.len();
        let n = matrix[0].len();
        let mut row_min = vec![100001; m];
        let mut col_max = vec![0; n];

        for i in 0..m {
            for j in 0..n {
                row_min[i] = row_min[i].min(matrix[i][j]);
                col_max[j] = col_max[j].max(matrix[i][j]);
            }
        }

        row_min.drain(..).filter(|x| col_max.contains(x)).collect()
    }
}