1380. Lucky Numbers in a Matrix

2D array use transpose

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.

# @param {Integer[][]} matrix
# @return {Integer[]}
def lucky_numbers (matrix)
  matrix.transpose.map {|row| row.max } & matrix.map {|col| col.min }
end