Number of 1 Bits

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

For example, the 32-bit integer ’11’ has binary representation 00000000000000000000000000001011, so the function should return 3.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

## https://code.dennyzhang.com/number-of-1-bits ## Baisc Ideas: Each time n & (n-1) will remove one 1 bit ## Complexity: Time O(k), k is most many 1 bits it has. Space O(1) class Solution(object): def hammingWeight(self, n): """ :type n: int :rtype: int """ res = 0 while n != 0: n = n & (n-1) res += 1 return res def hammingWeight_v1(self, n): """ :type n: int :rtype: int """ count = 0 while n != 0: if (n % 2) == 1: count = count + 1 n = n /2 return count