Lucky Numbers in a Matrix

Given an m x 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]
Explanation: 7 is the only lucky number since it is the minimum in its row and the maximum in its column.

 

Constraints:

• m == mat.length
• n == mat[i].length
• 1 <= n, m <= 50
• 1 <= matrix[i][j] <= 105.
• All elements in the matrix are distinct.

SOLUTION:

class Solution:
    def luckyNumbers (self, matrix: List[List[int]]) -> List[int]:
        m = len(matrix)
        n = len(matrix[0])
        luckyRows = set()
        luckyCols = set()
        for i in range(m):
            j = min(range(n), key = lambda x: matrix[i][x])
            luckyRows.add((i, j))
        for j in range(n):
            i = max(range(m), key = lambda x: matrix[x][j])
            luckyCols.add((i, j))
        lucky = set.intersection(luckyRows, luckyCols)
        return [matrix[i][j] for i, j in lucky]