[leetcode-476-Number Complement]

最新推荐文章于 2018-10-08 14:18:40 发布

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最新推荐文章于 2018-10-08 14:18:40 发布

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原文链接：http://www.cnblogs.com/hellowooorld/p/6786456.html

本文介绍了一种求正整数补码的有效算法。通过计算输入数值的二进制位数并利用位运算，快速得出补码结果。文章提供了具体实现代码，并通过两个实例解释了算法的工作原理。

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.

思路：

统计num对应的二进制所占的位数n，然后用2ⁿ-1 -num即可。

int findComplement(int num)
{
   int NUM = num;
    int tmp =1;
    while(num)
    {
        num>>=1;
        tmp <<=1;
    }
    return  tmp - NUM -1;
}