题目描述：

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 < 231.

Example:

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Input: x = 1, y = 4

Output: 2

Explanation:
1   (0 0 0 1)
4   (0 1 0 0)
       ↑   ↑

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

把两个数异或之后看结果有多少个1.

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class Solution {
public:
    int hammingDistance(int x, int y) {
        unsigned int z = x ^ y;
        int ans = 0;
        while(z > 0){
            if(z & 1) ans++;
            z >>= 1;
        }
        return ans;
    }
};