476. Number Complement

Posted 2020-09-01

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.

首先得到输入的整数的二进制有x位，再将输入的输与x位的1按位异或

C++（6ms）：

 1 class Solution {
 2 public:
 3     int findComplement(int num) {
 4        int a = ~0 ;
 5        while(num&a){
 6           a<<=1;
 7        }
 8        a=~a;
 9        return num^a;
10     }
11 };