Single Number II — LeetCode 137 Python Solution
MediumBit ManipulationArray
- Problem
- #137
- Pattern
- Bit Manipulation
- Reading time
- 2 min
- Source
- leetcode.com
The problem
Given an integer array nums where every element appears three times except for one, which appears exactly once. Find the single element and return it.
Example
- Input
- nums = [2,2,3,2]
- Output
- 3
Python solution
Python
class Solution:
def singleNumber(self, nums: List[int]) -> int:
ans = 0
for i in range(32):
cnt = sum(num >> i & 1 for num in nums)
if cnt % 3:
if i == 31:
ans -= 1 << i
else:
ans |= 1 << i
return ansComplexity
| Measure | Complexity |
|---|---|
| Time | O(n \times \log M), where n and M are the length of the array and the range of elements in the array, respectively |
| Space | O(1) auxiliary |
Pattern: Bit Manipulation
Use XOR, masks and the low-bit trick to replace whole data structures with an integer. LeetCode 137. Single Number II 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 a study list
This problem is on Top Interview 150.
Frequently asked questions
- How hard is LeetCode 137. Single Number II?
- LeetCode 137. Single Number II is rated Medium on LeetCode.
- What is the time complexity of LeetCode 137. Single Number II?
- The Python solution on this page runs in O(n \times \log M), where n and M are the length of the array and the range of elements in the array, respectively.
- What is the space complexity of LeetCode 137. Single Number II?
- The Python solution on this page uses O(1) auxiliary space.
- What topics does LeetCode 137. Single Number II cover?
- LeetCode 137. Single Number II is tagged Bit Manipulation and Array on LeetCode.