LeetCode191 Number of 1 bits

also knowns as hamming distance:

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int res = 0;
        for (int i = 0; i < 32; i++) { //为什么在这里用while(n>0)不行？
            res += n&1; //如果n的最右边的一位是0， res+0, 如果最右边一位是1 则res是1
            n >>= 1;
        }
        return res;
    }
}