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:

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.

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;
    }
}