476. Number Complement

Question:

Given a positive integer, output its complement number. The complement strategy is to flip the bits of its 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.

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.

Solution:

class Solution {
public:
    int findComplement(int num) {
        int judge;
        for(int i = 0; i < 32; i ++) {
            judge = 1 << i;
            if (judge > num) {
                break;
            }
        }

        return num xor (judge - 1);
    }
};

题目直达：https://leetcode.com/problems/number-complement/#/description