0681. Next Closest Time

https://leetcode.com/problems/next-closest-time

Description

Given a time represented in the format "HH:MM", form the next closest time by reusing the current digits. There is no limit on how many times a digit can be reused.

You may assume the given input string is always valid. For example, "01:34", "12:09" are all valid. "1:34", "12:9" are all invalid.

Example 1:

**Input:** time = "19:34"
**Output:** "19:39"
**Explanation:** The next closest time choosing from digits **1**, **9**, **3**, **4**, is **19:39**, which occurs 5 minutes later.
It is not **19:33**, because this occurs 23 hours and 59 minutes later.

Example 2:

**Input:** time = "23:59"
**Output:** "22:22"
**Explanation:** The next closest time choosing from digits **2**, **3**, **5**, **9**, is **22:22**.
It may be assumed that the returned time is next day's time since it is smaller than the input time numerically.

Constraints:

• time.length == 5

• time is a valid time in the form "HH:MM".

• 0 <= HH < 24

• 0 <= MM < 60

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