5356_luck_number_in_matrix.py

'''

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.

'''
class Solution(object):
    def luckyNumbers(self, matrix):
        min_nums_in_rows = set()
        max_nums_in_cols = set()
        for row in matrix:
            min_nums_in_rows.add(min(row))
        for i in range(len(matrix[0])):
            col = [matrix[j][i] for j in range(len(matrix))]
            max_nums_in_cols.add(max(col))
        result = min_nums_in_rows.intersection(max_nums_in_cols)

        return list(result)

s = Solution()
m = [[3,7,8],[9,11,13],[15,16,17]]
print(s.luckyNumbers(m))