1009 Complement of Base 10 Integer.py

#!/usr/bin/python3
"""
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.

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:
0 <= N < 10^9
"""


class Solution:
    def bitwiseComplement(self, N: int) -> int:
        """
        invert the bit, and the mask it
        """
        mask = 1
        cur = N
        while cur >> 1:
            cur >>= 1
            mask <<= 1
            mask += 1

        return ~N & mask