1380-lucky-numbers-in-a-matrix.py

"""
Problem Link: https://leetcode.com/problems/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.
"""\
# Time Complexity: O(len(row) * len(col))
# Space Complexity: O(len(row))
class Solution:
    def luckyNumbers (self, matrix: List[List[int]]) -> List[int]:
        res = []
        numbers = set()
        for row in range(len(matrix)):
          min_number = matrix[row][0]
          for j in range(1,len(matrix[row])):
            if matrix[row][j] < min_number:
              min_number = matrix[row][j]
          numbers.add(min_number)
        
        for col in range(len(matrix[0])):
          max_number = matrix[0][col]
          for j in range(len(matrix)):
            if matrix[j][col] > max_number:
              max_number = matrix[j][col]
          if max_number in numbers:
              res.append(max_number)
        return res