Number of 1 Bits — LeetCode 191 Python Solution
EasyBit ManipulationDivide and Conquer
- Problem
- #191
- Pattern
- Bit Manipulation
- Reading time
- 2 min
- Source
- leetcode.com
The problem
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).
Python solution
Python
class Solution:
def hammingWeight(self, n: int) -> int:
ans = 0
while n:
n &= n - 1
ans += 1
return ansComplexity
| Measure | Complexity |
|---|---|
| Time | O(n) |
| Space | O(1) auxiliary |
Pattern: Bit Manipulation
Use XOR, masks and the low-bit trick to replace whole data structures with an integer. LeetCode 191. Number of 1 Bits is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Bit Manipulation.
The bit manipulation guide has the Python template for the pattern and the 194 LeetCode problems that use it.
Related problems
On study lists
This problem is on Blind 75, NeetCode 150 and Top Interview 150.
Frequently asked questions
- How hard is LeetCode 191. Number of 1 Bits?
- LeetCode 191. Number of 1 Bits is rated Easy on LeetCode.
- What is the time complexity of LeetCode 191. Number of 1 Bits?
- The Python solution on this page runs in O(n).
- What is the space complexity of LeetCode 191. Number of 1 Bits?
- The Python solution on this page uses O(1) auxiliary space.
- What topics does LeetCode 191. Number of 1 Bits cover?
- LeetCode 191. Number of 1 Bits is tagged Bit Manipulation and Divide and Conquer on LeetCode.