# Complement of Base 10 Integer

## [Complement of Base 10 Integer](https://leetcode.com/problems/complement-of-base-10-integer)

Every non-negative integer `N` has a binary representation.  For example, `5` can be represented as `"101"` in binary, `11` as `"1011"` in binary, and so on.  Note that except for `N = 0`, there are no leading zeroes in any binary representation.

The *complement* of a binary representation is the number in binary you get when changing every `1` to a `0` and `0` to a `1`.  For example, the complement of `"101"` in binary is `"010"` in binary.

For a given number `N` in base-10, return the complement of it's binary representation as a base-10 integer.

1.

**Example 1:**

```

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

**Example 2:**

```

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

**Example 3:**

```

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

**Note:**

1. `0 <= N < 10^9`
2. This question is the same as 476: <https://leetcode.com/problems/number-complement/>

## Solutions

### 🧠 Cpp

```cpp
class Solution
{
public:
    //O(1) solution
    int bitwiseComplement(int N)
    {
        if(N == 0)
            return 1;
        //leading_zeros
        const size_t LZ =  __builtin_clz(N); 
        return (~(N << LZ)) >> LZ;
    }
};
```