LeetCode: Number Complement

LeetCode: 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:

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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:

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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.
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public class Solution {
    public int findComplement(int num) {
        double x = Math.log(num)/Math.log(2)+1;
        int length = (int) Math.floor(x);
        int result = 0;
        for (int i = 0; i < length; i++) {
            int mask = 1 << i;
            if ((num & mask) == 0) {
                result+= mask;
            }
        }
        return result;
    }
}