1
/**
2
 * Definition for a binary tree node.
3
 * function TreeNode(val, left, right) {
4
 *     this.val = (val===undefined ? 0 : val)
5
 *     this.left = (left===undefined ? null : left)
6
 *     this.right = (right===undefined ? null : right)
7
 * }
8
 */
9
/**
10
 * @param {TreeNode} root
11
 * @param {TreeNode} subRoot
12
 * @return {boolean}
13
 */
14
var isSubtree = function (root, subRoot) {
15
  if (subRoot === null) return true;
16
  if (root === null) return false;
17

18
  if (isSameTree(root, subRoot)) {
19
    return true;
20
  }
21

22
  return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot);
23
};
24

25
function isSameTree(root, subRoot) {
26
  if (root === null && subRoot === null) {
27
    return true;
28
  }
29

30
  if ((root && subRoot === null) || (root === null && subRoot)) {
31
    return false;
32
  }
33

34
  if (root.val !== subRoot.val) {
35
    return false;
36
  }
37
  return (
38
    isSameTree(root.left, subRoot.left) && isSameTree(root.right, subRoot.right)
39
  );
40
}