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.
实现：
1 class Solution {
2 public:
3 int hammingWeight(uint32_t n) {
4 int count = 0;
5 while(n)
6 {
7 count++;
8 n = n & (n - 1);
9 }
10 return count;
11 }
12 };