Lucky Numbers in a Matrix

Description

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.

Solution(javascript)

/**
 * @param {number[][]} matrix
 * @return {number[]}
 */
const luckyNumbers = function (matrix) {
  const rowMins = matrix.map(rows => Math.min(...rows))

  const result = []
  for (let column = 0; column < matrix[0].length; column++) {
    let max = -Infinity
    let currentRow = 0
    for (let row = 0; row < matrix.length; row++) {
      if (matrix[row][column] > max) {
        max = matrix[row][column]
        currentRow = row
      }
    }
    if (max === rowMins[currentRow]) {
      result.push(max)
    }
  }
  return result
}