LeetCode——Number Complement

LeetCode——Number Complement

Question

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

Note:
The given integer is guaranteed to fit within the range of a 32-bit signed integer.
You could assume no leading zero bit in the integer’s binary representation.

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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.

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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.

具体实现

class Solution {
public:
    int findComplement(int num) {
        int i = 0;
        while (num >= pow(2, i)) {
            i++;
        }
        int value = pow(2, i > 0 ? i : 1) - 1;
        return value ^ num;

    }
};