LeetCode in Kotlin

949. Largest Time for Given Digits

Medium

Given an array arr of 4 digits, find the latest 24-hour time that can be made using each digit exactly once.

24-hour times are formatted as "HH:MM", where HH is between 00 and 23, and MM is between 00 and 59. The earliest 24-hour time is 00:00, and the latest is 23:59.

Return the latest 24-hour time in "HH:MM" format. If no valid time can be made, return an empty string.

Example 1:

Input: arr = [1,2,3,4]

Output: “23:41”

Explanation: The valid 24-hour times are “12:34”, “12:43”, “13:24”, “13:42”, “14:23”, “14:32”, “21:34”, “21:43”, “23:14”, and “23:41”. Of these times, “23:41” is the latest.

Example 2:

Input: arr = [5,5,5,5]

Output: “”

Explanation: There are no valid 24-hour times as “55:55” is not valid.

Constraints:

• arr.length == 4
• 0 <= arr[i] <= 9

Solution

class Solution {
    fun largestTimeFromDigits(arr: IntArray): String {
        val buf = StringBuilder()
        var maxHour: String? = ""
        for (i in 0..3) {
            for (j in 0..3) {
                if (i != j) {
                    val hour = getTime(arr, i, j, 23, false)
                    val min = getTime(arr, i, j, 59, true)
                    if (hour != null && min != null && hour > maxHour!!) {
                        buf.setLength(0)
                        buf.append(hour).append(':').append(min)
                        maxHour = hour
                    }
                }
            }
        }
        return buf.toString()
    }

    private fun getTime(arr: IntArray, i: Int, j: Int, limit: Int, exclude: Boolean): String? {
        var n1 = -1
        var n2 = -1
        for (k in 0..3) {
            if (exclude && k != i && k != j || !exclude && (k == i || k == j)) {
                if (n1 == -1) {
                    n1 = arr[k]
                } else {
                    n2 = arr[k]
                }
            }
        }
        var s1: String? = n1.toString() + n2
        var s2: String? = n2.toString() + n1
        var v1 = s1!!.toInt()
        if (v1 > limit) {
            v1 = -1
            s1 = null
        }
        var v2 = s2!!.toInt()
        if (v2 > limit) {
            v2 = -1
            s2 = null
        }
        return if (v1 >= v2) s1 else s2
    }
}

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