476. Number Complement（补数）

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.

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.

思路：给定一个正整数，输出它的补数。补数的策略是通过翻转二进位表示。
1.求出该数的二进制位数；
2.通过给定数num和相同位数的二进制数（全为1）进行异或，即可求出补数。

 public int findComplement(int num) {

            int ans = 0;//the count of the num's bits

            int temp = num;//copy of the num

            while(temp != 0){

                ans++;

                temp /= 2;

            }

            return num ^ (int)(Math.pow(2,ans)-1);

    }

pow() 函数用来求 x 的 y 次幂（次方），其原型为：
double pow(double x, double y);

巴特西

476. Number Complement（补数）

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