## 476. Number Complement

Given a **positive** integer `num`

, output its complement number. The complement strategy is to flip the bits of its binary representation.

**Example 1:**

Input:num = 5Output:2Explanation:The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.

**Example 2:**

Input:num = 1Output:0Explanation:The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.

**Constraints:**

- The given integer
`num`

is guaranteed to fit within the range of a 32-bit signed integer. `num >= 1`

- You could assume no leading zero bit in the integerâ€™s binary representation.
- This question is the same as 1009: https://leetcode.com/problems/complement-of-base-10-integer/

## Rust Solution

```
struct Solution;
impl Solution {
fn find_complement(num: i32) -> i32 {
let mut mask = !0;
while mask & num != 0 {
mask <<= 1;
}
!mask & !num
}
}
#[test]
fn test() {
assert_eq!(Solution::find_complement(5), 2);
assert_eq!(Solution::find_complement(1), 0);
}
```

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