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

分析：本题求一个整型数的二进制补数，即对应二进制位取反。

思路：数拆成二进制，同时进行运算，对有效位取反，再组装成十进制数即可。

JAVA CODE

class Solution {
    public int findComplement(int num) {
　　　　　//将二进制数组(an ... a3 a2 a1 a0)装成十进制。a0+2*(a1+2*(a2+...2*(an+0))) 用递归的思想可以得到很简洁的代码（注意取反操作）。
        return (1-num%2)+2*(num==1?0:findComplement(num/2));
    }
}