476. Number Complement

QUESTION:

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.

EXPLANATION:

其实逻辑很简单，就是取反之后取到之前的位数，然后转化成数字就可以了，在网上看了下别人的方法，一行的好多，忽然觉得自己的位运算

SOLUTION:

public int findComplement(int num) {
        String numstring = Integer.toBinaryString(num);
        String complementnumstring = Integer.toBinaryString(~num);
        String result = complementnumstring.substring(complementnumstring.length()-numstring.length(),complementnumstring.length());
        int intresult = Integer.valueOf(result,2);
        return intresult;
    }
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