題目:
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.
翻譯:
給定一個正數,輸出它的補數。補數的策略是翻轉其二進制表示的位。
注意:
- 給定的數字保證是符合32-位有符號數的範圍。
- 你可以假設在數字的二進制表示前面沒有前置零位。
例子1:
輸入: 5 輸出: 2 解釋: 5的二進制表示是101(沒有前置零位),並且它的補數爲010.所以你需要輸出2。
例子2:
輸入: 1 輸出: 0 解釋: 1的二進制表示爲1(沒有前置零位),並且它的補數爲0,所以你需要輸出0。
思路:
主要需要考慮的是沒有前置零的問題,因此,我們先得到0的補數mask,然後通過和給定的數字num比較,將除了前置零位的mask的其他位都置爲0,最後用num的補數和mask進行異或。
C++代碼(Visual Studio 2017):
#include "stdafx.h"
#include <iostream>
using namespace std;
class Solution {
public:
int findComplement(int num) {
unsigned mask = ~0;
while (num&mask)
mask <<= 1;
return ~num^mask;
}
};
int main()
{
Solution s;
int num = 5;
int result;
result = s.findComplement(num);
cout << result;
return 0;
}