[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;}};