476. 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.

大致意思是把一个整数转成2进制，然后按位取反，再转成10进制并输出

class Solution {
    public int findComplement(int num) {
        String temp = Integer.toBinaryString(num);
        int result = 0;
        for(int i=0;i<temp.length();i++)
        {
            if(temp.charAt(i)=='0')
            {
                result = result+(int)Math.pow(2,temp.length()-i-1);
            }
        }
        return result;
    }
}