191.Numberof1Bits.py

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

    Note:
        - Note that in some languages such as Java, there is 
          no unsigned integer type. In this case, the input 
          will be given as a signed integer type. It should 
          not affect your implementation, as the integer's 
          internal binary representation is the same, whether 
          it is signed or unsigned.
        - In Java, the compiler represents the signed integers 
          using 2's complement notation. Therefore, in Example 
          3 above, the input represents the signed integer. -3.

    Follow up: If this function is called many times, how 
    would you optimize it?

    Example:
    Input: n = 00000000000000000000000000001011
    Output: 3
    Explanation: The input binary string 
                00000000000000000000000000001011 has a total 
                of three '1' bits.

    Example:
    Input: n = 00000000000000000000000010000000
    Output: 1
    Explanation: The input binary string 
                00000000000000000000000010000000 has a total 
                of one '1' bit.

    Example:
    Input: n = 11111111111111111111111111111101
    Output: 31
    Explanation: The input binary string 
                11111111111111111111111111111101 has a total 
                of thirty one '1' bits.

    Constraints:
        - The input must be a binary string of length 32
'''
#Difficulty: Easy
#601 / 601 test cases passed.
#Runtime: 32 ms
#Memory Usage: 14.1 MB

#Runtime: 32 ms, faster than 62.92% of Python3 online submissions for Number of 1 Bits.
#Memory Usage: 14.1 MB, less than 70.08% of Python3 online submissions for Number of 1 Bits.

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