Detect and Remove Loop in a Linked List

detect-and-remove-loop-in-a-linked-list.js

// https://www.geeksforgeeks.org/detect-and-remove-loop-in-a-linked-list/
function printList(root) {
  let tmp = root;
  let arr = [];
  while (tmp) {
    arr.push(tmp.val);
    tmp = tmp.next;
  }
  return arr;
}
class Node {
  constructor(val, next) {
    this.val = val;
    this.next = next;
  }
}

function printNNodes(N) {
  return function printNodes(root) {
    let tmp = root;
    let arr = [];
    let idx;
    for (idx = 0; idx < N; idx++) {
      if (tmp) {
        arr.push(tmp.val);
        tmp = tmp.next;
      }
    }
    return arr;  
  }
}

function removeLoopInNodes(root) {
  let tmp = root;
  const nextPointerStack = [];
  while (tmp) {
    if (nextPointerStack.indexOf(tmp.next) >= 0) tmp.next = null;
    nextPointerStack.push(tmp.next);
    tmp = tmp.next;
  }
  return root;
}

const print6Nodes = printNNodes(6);
const ex1 = new Node(1, new Node(3, new Node(4)));
// Looped
ex1.next.next.next = ex1.next;
console.log(print6Nodes(ex1).join(',') === '1,3,4,3,4,3');
removeLoopInNodes(ex1);
console.log(print6Nodes(ex1).join(',') === '1,3,4');

const ex2 = new Node(1, new Node(8, new Node(3, new Node(4))));
// Looped
ex2.next.next.next.next = ex2.next;
console.log(print6Nodes(ex2).join(',') === '1,8,3,4,8,3');
removeLoopInNodes(ex2);
console.log(print6Nodes(ex2).join(',') === '1,8,3,4');