476. Number Complement (Easy)

https://leetcode.com/problems/number-complement/

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.

Solutions

class Solution {

    public int findComplement(int num) {
        if (num == 0) {
            return 1;
        }

        int ans = 0;

        int pow = 0;
        int tmp = num;
        while (tmp > 0) {
            if (tmp % 2 == 0) {
                ans += 1 << pow;
            }

            pow++;
            tmp = tmp / 2;
        }

        return ans;
    }
}

Incorrect Solutions

References