Complement of Base 10 Integer

Problem

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.

Constraints

• 0 <= n <= 109

Solution

The problem Complement of Base 10 Integer is the same as Number Complement.

Implementation

static const int fast_io = []()
{
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    return 0;
}();

class Solution
{
  public:
    int bitwiseComplement(int n)
    {
        if (n == 0)
            return 1;

        unsigned int mask = n;
        while (mask & (mask - 1))
            mask &= mask - 1;
        mask = (mask << 1) - 1;

        return n ^ mask;
    }
};