01_位1的个数

class Solution(object):
    def hammingWeight(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n < 0:
            return 0
        return bin(n).count('1')


# leetcode 最优解
class Solution2(object):
    def hammingWeight(self, n):
        """
        :type n: int
        :rtype: int
        """
        count = 0
        while(n != 0):
            n = n & (n - 1)
            count = count + 1
        return count