476. Number Complement

Given a positive integer, output its complement number. The complement strategy is to flip the bits of its 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.

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.
3. This question is the same as 1009: https://leetcode.com/problems/complement-of-base-10-integer/

class Solution {
    public int findComplement(int num) {
        String s = Integer.toBinaryString(num);
        String sb = "";
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) == '0') sb += '1';
            else sb += '0';
        }
        return Integer.parseInt(sb,2);
    }
}

integer的补码然后再变成integer，学到了新的method==Integer.toBinaryString(Integer)

以及Integer.parseInte(String, hex)