[LeetCode]476. Number Complement

题目

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

Note:

1. The given integer is guaranteed to fit within the range of a 32-bit signed integer.
2. You could assume no leading zero bit in the integer’s binary representation.

Example 1:

Input: 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: 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.

难度

Easy

方法

从低位到高位，取出num的每一位求反，保存至result的相同位中

python代码

class Solution(object):
    def findComplement(self, num):
        """
        :type num: int
        :rtype: int
        """
        i = 1
        result = 0
        while i <= num:
            result |= (i & num) ^ i
            i <<= 1
            
        return result

assert Solution().findComplement(5) == 2
assert Solution().findComplement(1) == 0