476. Number Complement-数字的补数

Given a positive integer num, output its complement number. The complement strategy is to flip the bits of its binary representation.

Example 1:
Input: num = 5
Output: 2
Explanation: The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.

Example 2:
Input: num = 1
Output: 0
Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.

Constraints:
The given integer num is guaranteed to fit within the range of a 32-bit signed integer.
num >= 1
You could assume no leading zero bit in the integer’s binary representation.
This question is the same as 1009: https://leetcode.com/problems/complement-of-base-10-integer/

Solution in python:

class Solution:
    def findComplement(self, num: int) -> int:
        n = num
        q = 0
        while n > 0:
            q <<= 1
            q += 1
            n >>= 1
        return num^q