1var assert = require('assert');
2
3// iterative
4function reverseList(head) {
5  if (head.length < 2) {
6    return;
7  }
8
9  let newHead = null;
10  while (head != null) {
11    let nextNode = head.next;
12    head.next = newHead;
13    newHead = head;
14    head = nextNode;
15  }
16  return newHead;
17}
18
19// recursive
20function reverseList(head) {
21  if (!head || !head.next) {
22    return head;
23  }
24
25  let rest = reverseList(head.next);
26
27  head.next.next = head;
28  delete head.next;
29  return rest;
30}
31
32function Node(val) {
33  this.val = val;
34  this.next = null;
35}
36
37function LinkedListNode(val) {
38  this.val = val;
39  this.next = null;
40}
41
42var list1 = new LinkedListNode(3);
43var nodes1 = [4, 5, 6, 7, 8, 9, 10];
44createNodes(list1, nodes1);
45
46var list2 = new LinkedListNode(1);
47var nodes2 = [2, 3, 4, 5, 6, 7, 8];
48createNodes(list2, nodes2);
49
50function createNodes(head, nodes) {
51  for (let i = 0; i < nodes.length; i++) {
52    var newNode = new LinkedListNode(nodes[i]);
53    head.next = newNode;
54    head = newNode;
55  }
56}
57
58try {
59  var reversed = reverseList(list1);
60  assert.deepEqual(
61    listToString(reversed),
62    '10 -> 9 -> 8 -> 7 -> 6 -> 5 -> 4 -> 3'
63  );
64
65  console.log(
66    'PASSED: Reversing linked list `3 -> 4 -> 5 -> 6 -> 7 -> 8 -> 9 -> 10` should return `10 -> 9 -> 8 -> 7 -> 6 -> 5 -> 4 -> 3`'
67  );
68} catch (err) {
69  console.log(err);
70}
71
72function listToString(head) {
73  var toPrint = [];
74  var currNode = head;
75  while (currNode) {
76    toPrint.push(currNode.val);
77    currNode = currNode.next;
78  }
79  return toPrint.join(' -> ');
80}