位运算（2）——Number of 1 Bits

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.

输入：32位整数

输出：二进制中1的个数

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int res = 0;
        while(n != 0) {
            /*if((n & 1) == 1) {  //超时
                res++;
                n >>= 1;
            } else {
                n >>= 1;
            }*/
            n &= (n-1); //消掉n最右边的1
            res++;
        }
        return res;
    }
}