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题目：

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as the Hamming weight).

For example, the 32-bit integer ’11' has binary representation 00000000000000000000000000001011, so the function should return 3.

unsigned integer： http://baike.baidu.com/view/6052699.htm

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
    
        int res=0;
        int k=0;
        for(int i=1;i<=32;i++)
        {
            res=n&1;
            if(res==1) k++;
            n=n>>1;        
            
        }
        return k;
    }
}