题解：我之前写的位运算模板

图1：

class Solution {
public:
    uint32_t lowbit(uint32_t x) {
        return x & -x;
    }
    int hammingWeight(uint32_t n) {
        int cnt = 0;
        while (n) {
            n -= lowbit(n);
            cnt ++;
        }
        return cnt;
    }
};