# 问题描述

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.`

# Python

python 中~操作是取补码, 此题取反

`class Solution(object):    def findComplement(self, num):        """        :type num: int        :rtype: int        """        return num ^ int(bin(num)[2:].replace("0","1"),2)`

# Java

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