461. Hamming Distance

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题目

The Hamming distance between two integers is the number of positions at which the corresponding bits are different.

Given two integers x and y, calculate the Hamming distance.

Note:
0 ≤ x, y < 2^31 .

Example:

Input: x = 1, y = 4

Output: 2

Explanation: 

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3
1   (0 0 0 1)    
4   (0 1 0 0)    
       ↑   ↑

The above arrows point to positions where the corresponding bits are different.

思路

题目说 y < 2^31 那写一个32次的循环，依次统计一共有多少个1就好。

代码

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//C++
int hammingDistance(int x, int y) {
    int result = 0;
    int s = x^y;
    for(int i = 0;i<32;i++) {
        if(s & 1 == 1) {
            result ++;
        }
        s = s>>1;
    }
    return result;
}

然后看到别人思路貌似有个比32次循环更快的方法：

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//C++
int hammingDistance(int x, int y) {
    int dist = 0, n = x ^ y;
    while (n) {
        ++dist;
        n &= n - 1;
    }
    return dist;
}