476. Number Complement

最新推荐文章于 2020-10-02 12:52:18 发布

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本文介绍了一种求正整数补数的有效算法。通过位运算实现补数计算，即翻转给定正整数二进制表示中的每一位。文中提供了一个具体的C++实现示例，包括如何处理边界情况。

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.

解题思路：用~取反，直接进行位运算

class Solution {
public:
    int findComplement(int num) {
        unsigned mask = ~0;
        while (num & mask)

         mask <<= 1;
        return ~mask & ~num;
    }
};