Number of 1 Bits

就是elements里面介绍的快速找最末尾1的方法

class Solution(object):
    def hammingWeight(self, n):
        """
        :type n: int
        :rtype: int
        """
        cur = n
        result = 0 
        while cur:
            result += 1
            cur &= (cur - 1)
        return result