LeetCode in Kotlin

1380. Lucky Numbers in a Matrix

Easy

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 {
    fun luckyNumbers(matrix: Array<IntArray>): List<Int> {
        val mini: MutableList<Int> = ArrayList()
        val maxi: MutableList<Int> = ArrayList()
        for (arr in matrix) {
            var min = Int.MAX_VALUE
            for (j in arr) {
                if (min > j) {
                    min = j
                }
            }
            mini.add(min)
        }
        val cols = matrix[0].size
        for (c in 0 until cols) {
            var max = Int.MIN_VALUE
            for (ints in matrix) {
                if (ints[c] > max) {
                    max = ints[c]
                }
            }
            maxi.add(max)
        }
        val res: MutableList<Int> = ArrayList()
        for (value in mini) {
            if (maxi.contains(value)) {
                res.add(value)
            }
        }
        return res
    }
}

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