leetcode之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.

解答

例子：a = 10001000

其中，a - 1变成10000111 a&(a-1) 变成10000000，再这样运算一次就可以结束，看了这个例子，思想也就理解了，复杂度是O(t)t是1的个数

class Solution {

public:

    int hammingWeight(uint32_t n) {

        int res = 0;

        while(n)

        {

            n = n & (n - 1);

            res ++;

        }

        return res;

    }

};