leetcode191. Number of 1 Bits

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Write a function that takes an unsigned integer and returns the number of '1' bits it has (also known as the Hamming weight).

Example 1:

Input: 11
Output: 3
Explanation: Integer 11 has binary representation 
00000000000000000000000000001011 

Example 2:

Input: 128
Output: 1
Explanation: Integer 128 has binary representation 00000000000000000000000010000000

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<思路>先将十进制数字转化为二进制，再数1的个数。学会使用count()方法。

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