// 1 2 3 4 5
//     ^   |
//     |___|

class Node {
  constructor(value, next = null) {
    this.value = value;
    this.next = next;
  }
}

function hasCycle(node) {
  let visited = new Set();
  for(let curr = node; curr != null; curr = curr.next) {
    if(visited.has(curr)) return true;
    visited.add(curr);
  }

  return false;
}

function hasCycleFloyd(node) {
  if(node === null) return false;
  let slow = node;
  let fast = node.next;

  while(fast !== null && fast.next !== null) {
    if(fast === slow) return true;
    slow = slow.next;
    fast = fast.next.next;
  }

  return false;
}


let node1 = new Node(1);
let node2 = new Node(2);
let node3 = new Node(3);
let node4 = new Node(4);
let node5 = new Node(5);

node1.next = node2;
node2.next = node3;
node3.next = node4;
node4.next = node5;
node5.next = node3;

console.log(`==> ${hasCycleFloyd(node1)}`)