Linked List Cycle
Explore how to identify a cycle in a linked list by applying the fast and slow pointer technique. This lesson teaches you to return true if a cycle exists, helping you understand a common pattern tested in coding interviews.
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Statement
Given the head of a linked list, determine whether the list contains a cycle. A cycle exists if a node in the list can be revisited by continuously following the next pointers. Return TRUE if a cycle is present; otherwise, return FALSE.
Constraints:
Let n be the number of nodes in a linked list.
-
n -
Node.value
Examples
Understand the problem
Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:
Linked List Cycle
What is the output if the following linked list is given as an input?
TRUE
FALSE
Figure it out!
We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.
Try it yourself
Implement your solution in the following coding playground.
// The first input of the test case is an array of values representing a linked list.// The second input is the index where the tail connects to form a cycle (or −1 if there's no cycle).// This index is used only to construct the linked list and is not passed to the function.// Definition for a Linked List node// class ListNode {// int val;// ListNode next;// // Constructor// public ListNode(int val) {// this.val = val;// this.next = null;// }// }import ds_v1.LinkedList.ListNode;import java.util.*;public class Solution{public static boolean detectCycle(ListNode head) {// Replace this placeholder return statement with your codereturn false;}}