Q191. Number of 1 Bits

直达：https://leetcode.com/problems/number-of-1-bits/description/

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as theHamming weight).

For example, the 32-bit integer ’11' has binary representation00000000000000000000000000001011, so the function should return 3.

Credits: Special thanks to@tsfor adding this problem and creating all test cases.

分析：

二进制中，n&(n-1)作用是将n的二进制表示中的最低位为1的改为0，每更改一次计数器+1，知道n=0停止。

C++代码

class Solution {
public:
    int hammingWeight(uint32_t n) {
        int res = 0;
        while(n){
            n &= n-1;
            res++;
        }
        return res;
    }
};