## 681. 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:time = "19:34"Output:"19:39"Explanation:The next closest time choosing from digits1,9,3,4, is19:39, which occurs 5 minutes later. It is not19:33, 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 digits2,3,5,9, is22:22. 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`

## Rust Solution

```
struct Solution;
impl Solution {
fn next_closest_time(time: String) -> String {
let h = time[..2].parse::<usize>().unwrap();
let m = time[3..].parse::<usize>().unwrap();
let a = h / 10;
let b = h % 10;
let c = m / 10;
let d = m % 10;
let set = 1 << a | 1 << b | 1 << c | 1 << d;
let mut found = false;
for _ in 0..2 {
for i in 0..24 {
for j in 0..60 {
if !found {
if i == h && j == m {
found = true;
}
} else {
let a = i / 10;
let b = i % 10;
let c = j / 10;
let d = j % 10;
let next_set = 1 << a | 1 << b | 1 << c | 1 << d;
if (next_set | set) == set {
return format!("{}{}:{}{}", a, b, c, d);
}
}
}
}
}
"".to_string()
}
}
#[test]
fn test() {
let time = "19:34".to_string();
let res = "19:39".to_string();
assert_eq!(Solution::next_closest_time(time), res);
let time = "23:59".to_string();
let res = "22:22".to_string();
assert_eq!(Solution::next_closest_time(time), res);
}
```

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