Algorithm Notes
Summary: Single Number — notes not yet curated.
Time: Estimate via loops/recurrences; common classes: O(1), O(log n), O(n), O(n log n), O(n^2)
Space: Count auxiliary structures and recursion depth.
Tip: See the Big-O Guide for how to derive bounds and compare trade-offs.
Big-O Guide
Source
"""
Single Number
TODO: Add problem description
"""
import random
from src.interview_workbook.leetcode._registry import register_problem
from src.interview_workbook.leetcode._types import Category, Difficulty
class Solution:
def solve(self, nums: list[int]) -> int:
"""Return the element that appears only once in the array where every other element appears twice."""
result = 0
for num in nums:
result ^= num
return result
def demo() -> str:
"""Run a deterministic demo for Single Number."""
random.seed(0)
sol = Solution()
test_values = [
[2, 2, 1],
[4, 1, 2, 1, 2],
[1],
]
print(f"Test values: {test_values}")
results = {str(lst): sol.solve(lst) for lst in test_values}
print(f"Final results: {results}")
return str(results)
register_problem(
id=136,
slug="single_number",
title="Single Number",
category=Category.BIT_MANIP,
difficulty=Difficulty.EASY,
tags=["array", "bit_manipulation"],
url="https://leetcode.com/problems/single-number/",
notes="",
)