# 1009. Complement of Base 10 Integer

#### Easy

***

The **complement** of an integer is the integer you get when you flip all the `0`'s to `1`'s and all the `1`'s to `0`'s in its binary representation.

* For example, The integer `5` is `"101"` in binary and its **complement** is `"010"` which is the integer `2`.

Given an integer `n`, return *its complement*.

 

**Example 1:**

```
Input: n = 5
Output: 2
Explanation: 5 is "101" in binary, with complement "010" in binary, which is 2 in base-10.
```

**Example 2:**

```
Input: n = 7
Output: 0
Explanation: 7 is "111" in binary, with complement "000" in binary, which is 0 in base-10.
```

**Example 3:**

```
Input: n = 10
Output: 5
Explanation: 10 is "1010" in binary, with complement "0101" in binary, which is 5 in base-10.
```

 

**Constraints:**

* `0 <= n < 109`

&#x20;

**Note:** This question is the same as 476: <https://leetcode.com/problems/number-complement/>

```python
class Solution:
    def bitwiseComplement(self, n: int) -> int:
        # Same as PB 476 : https://leetcode.com/problems/number-complement/
        if n == 0:
            return 1
        bit = 1
        while bit <= n:
            bit = bit << 1
        return (bit-1) ^ n
```