1var assert = require('assert');
2
3function invertTree(head) {
4  if (head) {
5    var temp = head.left;
6    head.left = head.right;
7    head.right = temp;
8
9    invertTree(head.left);
10    invertTree(head.right);
11  }
12
13  return head;
14}
15
16function Node(val) {
17  this.val = val;
18  this.left = null;
19  this.right = null;
20}
21
22// Regular binary trees
23var tree1 = new Node(4);
24tree1.left = new Node(1);
25tree1.right = new Node(3);
26
27var tree2 = new Node(5);
28tree2.left = new Node(10);
29tree2.left.left = new Node(17);
30tree2.left.right = new Node(3);
31tree2.right = new Node(8);
32
33// Binary search trees
34var tree3 = new Node(6);
35tree3.left = new Node(3);
36
37var tree4 = new Node(5);
38tree4.left = new Node(3);
39tree4.left.left = new Node(2);
40tree4.left.left.left = new Node(1);
41
42var tree5 = new Node(8);
43tree5.left = new Node(6);
44tree5.right = new Node(9);
45tree5.left.left = new Node(5);
46tree5.left.right = new Node(7);
47tree5.right.right = new Node(10);
48
49try {
50  assertIsFunction(invertTree, '`invertTree` should be a function');
51
52  console.log('PASSED: ' + '`invertTree` should be a function');
53} catch (err) {
54  console.log(err);
55}
56
57try {
58  var invertedTree1 = new Node(4);
59  invertedTree1.left = new Node(3);
60  invertedTree1.right = new Node(1);
61  assert.deepEqual(invertTree(tree1), invertedTree1);
62
63  console.log('PASSED: ' + '`tree1` should invert correctly');
64} catch (err) {
65  console.log(err);
66}
67
68function assertIsFunction(f) {
69  return typeof f === 'function';
70}