## 401. Binary Watch

A binary watch has 4 LEDs on the top which represent the **hours** (**0-11**), and the 6 LEDs on the bottom represent the **minutes** (**0-59**).

Each LED represents a zero or one, with the least significant bit on the right.

For example, the above binary watch reads "3:25".

Given a non-negative integer *n* which represents the number of LEDs that are currently on, return all possible times the watch could represent.

**Example:**

Input: n = 1

Return: ["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]

**Note:**

- The order of output does not matter.
- The hour must not contain a leading zero, for example "01:00" is not valid, it should be "1:00".
- The minute must be consist of two digits and may contain a leading zero, for example "10:2" is not valid, it should be "10:02".

## Rust Solution

```
struct Solution;
impl Solution {
fn read_binary_watch(num: i32) -> Vec<String> {
let mut res: Vec<String> = vec![];
for i in 0..11 {
for j in 0..60 {
if i32::count_ones(i) + i32::count_ones(j) == num as u32 {
res.push(format!("{}:{:02}", i, j));
}
}
}
res
}
}
#[test]
fn test() {
let num = 1;
let mut res: Vec<String> =
vec_string!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"];
res.sort_unstable();
assert_eq!(Solution::read_binary_watch(num), res);
}
```

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