[leetcode]Bit Manipulation-476. Number Complement

Posted 2020-10-20 chenhan05

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.

class Solution {
    public:
        int findComplement(int num) {
            long int flag = 1;
            long int res = 0;
            while(flag && flag <= num){
                int t = flag&num;
                if(t == 0){
                    res |= flag;
                }

                flag = flag << 1;
            }
            return res;
        }
    };