100. detect circle in linked list

easy  - accepted / - tried

A Singly Linked List is a bunch of nodes linked in one direction.

class Node {  val: any  next: Node  constructor(val: any, next:Node) {    this.val = val    this.next = next  }}const node2 = new Node(2)const node1 = new Node(1, node2) // connect 1 -> 2

A Node might link to a node before it, thus creating a circle.

Can you write a function to detect it?

Follow-up

What is the space cost for your approach? Can you solve it without extra space?

Bugfree ordinary solution is better than buggy fancy ones.

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