476. Number Complement

Problem Statement

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: 5Output: 2Explanation: 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: 1Output: 0Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.

Thinking

题目的意思是将一个整数的二进制全部反转。看代码吧，感觉不太好叙述。

Solution

class Solution {public:    int findComplement(int num) {        unsigned int mask = ~0;        while (num & mask) mask <<= 1;        return ~mask & ~num;    }};