# LeetCode 681. Next Closest Time

## Description

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

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: "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: "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.```

## Explanation

Simulate the clock going forward by one minute. Each time it moves forward, if all the digits are allowed, then return the time.

## Python Solution

``````class Solution:
def nextClosestTime(self, time: str) -> str:
current = 60 * int(time[:2]) + int(time[3:])

for i in range(current + 1, current + 1441):
minutes = i % 1440
h, m = minutes // 60, minutes % 60

result = "{:02d}:{:02d}".format(h, m)

if set(result) <= set(time):
break

return result``````
• Time Complexity: ~N
• Space Complexity: ~1

where N is a number of characters in the input string.