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.

计算一个整数中1的个数。通过位运算，每次右移一位，判断是否为1，如果为1计数器加1，代码如下：

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