题目要求

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.

题目分析及思路

题目给出一个正整数，要求得到它的complement number。complement number是先对原正整数取二进制，然后各位取反，最后再化为十进制的数。可以先获得原正整数的各位数，然后与1依次异或，将结果乘以权并求和。

python代码

class Solution:

def findComplement(self, num: 'int') -> 'int':

b = []

res = 0

while num:

b.append(num % 2)

num //= 2

for i in range(len(b)):

b[i] ^= 1

res += (b[i] * math.pow(2, i))

return int(res)