LeetCode之Number Complement

1、题目

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.

2、代码实现

public class Solution {

   public int findComplement(int num) {

    if (num <= 0)

     return 0;

    String result = "";

    while (num > 0) {

     result += num % 2;

     num = num / 2;

    }

    int length = result.length();

    int lastResult = 0;

    for (int i = 0; i < length - 1; ++i) {

     if (result.charAt(i) == '0') {

      int temp = (int) Math.pow(2, i);

      lastResult += temp;

     }

    return lastResult;

   }

}