LeetCode 141: Linked List Cycle — Step-by-Step Visual Trace

Easy — Linked List | Two Pointers | Hash Table The Problem Given the head of a linked list, determine if the linked list has a cycle in it. A cycle exists if there is some node in the list that can be reached again by continuously following the next pointer. Approach Uses Floyd's Cycle Detection Algorithm (tortoise and hare) with two pointers moving at different speeds. If there's a cycle, the fast pointer will eventually meet the slow pointer; if there's no cycle, the fast pointer will reach the end. Time: O(n) · Space: O(1) Code class Solution : def hasCycle ( self , head : ListNode ) -> bool : if not head or not head . next : return False slow = head fast = head . next while slow != fast : if not fast or not fast . next : return False slow = slow . next fast = fast . next . next return True Watch It Run TraceLit — See exactly where your code breaks Paste your LeetCode solution and see every pointer, variable, and data structure update step by step. tracelit.dev Open interactive visu