[leetcode][bit] Number of 1 Bits

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.

class Solution {
public:
int hammingWeight(uint32_t n) {
//n&(n-1)将n从低位开始的第一个1置0其他位保持不变
int cnt = 0;
while (n){
++cnt;
n = n&(n - 1);
}
return cnt;
}
};