LeetCode-191 Number of 1 Bits

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

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.
1、将32位分别与1相与，统计1的个数（8ms）
class Solution {

public:

    int hammingWeight(uint32_t n) {

        int mask = 1, sum = 0;

        for(int i = 0;i<32;i++){

            if((n & mask) != 0)

                sum++;

            mask = mask << 1;

        }

        return sum;

    }

};

2、利用整除2，统计余数为1的个数（4ms）

class Solution {

public:

    int hammingWeight(uint32_t n) {

        int sums = 0;

        while(n/2!=0){

            sums += n%2;

            n /= 2;

        }

        sums += n%2;

        return sums;

    }

};