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Practice Linked List Cycle

Read the task, work through the examples, and check your approach against the constraints. Use the original LeetCode task for coding and submissions.

Easy#141
LeetCode Problem

Linked List Cycle

Hash TableLinked ListTwo Pointers

Problem Statement

Given head, the head of a linked list, determine if the linked list has a cycle in it. There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the next pointer. Internally, pos is used to denote the index of the node that tail's next pointer is connected to. Note that pos is not passed as a parameter. Return true if there is a cycle in the linked list. Otherwise, return false. Follow up: Can you solve it using O(1) (i.e. constant) memory?

Source: Linked List Cycle on LeetCode. Use the original task for its coding environment and submissions.

Examples

# Example 1

Input
head = [3,2,0,-4], pos = 1
Output
true

# Example 2

Input
head = [1,2], pos = 0
Output
true

# Example 3

Input
head = [1], pos = -1
Output
false

Constraints

The number of the nodes in the list is in the range [0, 10^4].
-10^5 <= Node.val <= 10^5
pos is -1 or a valid index in the linked-list.

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