191 Number of 1 Bits

这题是计算hamming weight. 给的是一个32位的整数，计算这个整数的二进制表示中有多少个1, 所以我们需要做两件事,

• check if the last bit is 1
• use n & 1 = 1 to check if the last bit is 1 (same as check if it's odd)
• traverse the binary input by shift the bits to the right
• n >> 1 till n=0

Approach 1 Bit Manipulation

class Solution:
    def hammingWeight(self, n: int) -> int:
        # 1. check whether the last digit is 1
        #      n & 1 == 1 then yeahhhh
        # 2. traverse the bits
        #      n >> 1 until 
        counter = 0
        while n != 0:
            if n & 1 == 1:
                counter += 1            
            n = n >> 1

        return counter