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.
翻译:
给定一个正数,输出它的补数。补数的策略是翻转其二进制表示的位。
注意:
- 给定的数字保证是符合32-位有符号数的范围。
- 你可以假设在数字的二进制表示前面没有前置零位。
例子1:
输入: 5 输出: 2 解释: 5的二进制表示是101(没有前置零位),并且它的补数为010.所以你需要输出2。
例子2:
输入: 1 输出: 0 解释: 1的二进制表示为1(没有前置零位),并且它的补数为0,所以你需要输出0。
思路:
主要需要考虑的是没有前置零的问题,因此,我们先得到0的补数mask,然后通过和给定的数字num比较,将除了前置零位的mask的其他位都置为0,最后用num的补数和mask进行异或。
C++代码(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; }