0949. Largest Time for Given Digits

https://leetcode.com/problems/largest-time-for-given-digits

Description

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.

Example 3:

**Input:** arr = [0,0,0,0]
**Output:** "00:00"

Example 4:

**Input:** arr = [0,0,1,0]
**Output:** "10:00"

Constraints:

• arr.length == 4

• 0 <= arr[i] <= 9

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