March-191. The number of bits 1

class Solution:
    def hammingWeight(self, n: int) -> int:

        #将整数转化为二进制
        res = 0 
        while n>0:
            res+=(n%2)
            n = n//2
        return res

        #n&n-1会把最后一个1变为0
        ret = 0
        while n:
            n &= n - 1
            ret += 1
        return ret

        return bin(n).count('1')

•  The method of converting integers to binary, counting the number of ones
•  Use n&n-1 to change the last digit to 1 to count the number of 1s
•  Use the bin(n) API to directly convert integers to binary strings and count the number of 1