Python实现"数字的补数"的两种方法

给定一个整数，返回它的补数.补数策略针对整数的二进制位
注意：
给定的整数最大为32位
假设二进制不包含前导0
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.

1、利用bin()方法将整数转为二进制字符串，用for循环对字符串取反，用int( , 2)方法将取反后的字符串转为整数

def findComplement(self, num):
        """
        :type num: int
        :rtype: int
        """
        newBit = ""
        for i in bin(num)[2:]:
            newBit += "1" if i == "0" else "0"
        return int("0b" + newBit, 2)

优雅写法（参考他人）

return int("".join(map(lambda ch: '1' if ch=='0' else '0',bin(num)[2:])),2) 

2、取sum整数2的对数，向下取整+1获得x，计算2的x次幂-sum整数-1获得结果（参考他人）

def findComplement(self, num):
        """
        :type num: int
        :rtype: int
        """
        x = math.floor(math.log(num, 2)) + 1
        return int(2**x) - num - 1

移位写法（参考他人）

def findComplement(self, num):
        """
        :type num: int
        :rtype: int
        """
        s = 1 
        while s<=num:
            s<<=1
        return (s-1)^num

算法题来自：https://leetcode-cn.com/problems/number-complement/description/