class Solution:
    def findComplement(self, n: int) -> int:
        if n == 0:
            return 1

        mask = n
        
        # Create mask of length matching num of bits
        # in n (taken from Hacker's Delight, Figure 3-1)
        mask |= mask >> 1    # \
        mask |= mask >> 2    #  \
        mask |= mask >> 4    #   |> Totalling 31 bits
        mask |= mask >> 8    #  /
        mask |= mask >> 16   # /
        
        # XOR 1 will flip the bit
        return n ^ mask