leetcode-python-位1的个数

1）调库count

class Solution:
    def hammingWeight(self, n: int) -> int:
        return bin(n).count('1')

2)按位与，n&n-1等于去掉倒数的第一个1

class Solution:
    def hammingWeight(self, n: int) -> int:
        result = 0
        while n:
            result += 1
            n = n & n-1
        return result