Algorithm Notes
Summary: Linked List Cycle — 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
"""
Linked List Cycle
TODO: Add problem description
"""
from src.interview_workbook.leetcode._registry import register_problem
from src.interview_workbook.leetcode._types import Category, Difficulty
class Solution:
def solve(self, *args):
"""
Detect if linked list has a cycle.
Args: head (ListNode)
Returns: bool
"""
head = args[0]
slow, fast = head, head
while fast and fast.next:
slow = slow.next
fast = fast.next.next
if slow == fast:
return True
return False
def demo():
"""Run a simple demonstration for Linked List Cycle problem."""
from src.interview_workbook.leetcode._nodes import ListNode
# Create a cycle list: 3 -> 2 -> 0 -> -4 -> back to 2
n1, n2, n3, n4 = ListNode(3), ListNode(2), ListNode(0), ListNode(-4)
n1.next, n2.next, n3.next, n4.next = n2, n3, n4, n2
print("Created linked list with cycle at node with value 2")
s = Solution()
result = s.solve(n1)
print(f"Cycle detected: {result}")
return f"Cycle detected: {result}"
register_problem(
id=141,
slug="linked_list_cycle",
title="Linked List Cycle",
category=Category.LINKED_LIST,
difficulty=Difficulty.EASY,
tags=["linked_list", "two_pointers"],
url="https://leetcode.com/problems/linked-list-cycle/",
notes="",
)