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.

解析：

一位位看那个位是1：

class Solution {
public:
    int hammingWeight(uint32_t n) {
        int i = 0;
        while (n)
        {
            i += n & 0x1;
            n >>= 1;
        }
 
        return i;
    }
};

法二：用-1后的n做与运算

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