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

Example 1:

Input: 11
Output: 3
Explanation: Integer 11 has binary representation 00000000000000000000000000001011 

Example 2:

Input: 128
Output: 1
Explanation: Integer 128 has binary representation 00000000000000000000000010000000

方法1:右移位32次

class Solution {
public:
    //移位32次，与1按位与，数有多少个1
    int hammingWeight(uint32_t n) {
        int count=0;
        for(int i=0;i<32;i++){
            if((n>>i)&1) count++;
        }
        return count;
    }
 };

方法2：不停消去最右边的1

class Solution {
public:
    //每执行n=n&(n-1)，就会使左右边的1变为0.
    int hammingWeight(uint32_t n) {
        int count=0;
        while(n){
            n=n&(n-1);
            count++;
        }
        return count;
    }
};