191. Number Of 1 Bits

Divide and Conquer Bit Manipulation

Problem - Number Of 1 Bits

Easy

Given a positive integer n, write a function that returns the number of set bits in its binary representation (also known as the Hamming weight).

 

Example 1:

Input: n = 11

Output: 3

Explanation:

The input binary string 1011 has a total of three set bits.

Example 2:

Input: n = 128

Output: 1

Explanation:

The input binary string 10000000 has a total of one set bit.

Example 3:

Input: n = 2147483645

Output: 30

Explanation:

The input binary string 1111111111111111111111111111101 has a total of thirty set bits.

 

Constraints:

• 1 <= n <= 231 - 1

 

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

Solutions

Python3

class Solution:
    def hammingWeight(self, n: int) -> int:
        result = 0
        while n:
            n -= n & -n
            result += 1
        return result

Submission Stats:

• Runtime: 0 ms (100.00%)
• Memory: 17.7 MB (51.14%)