572. Subtree of Another Tree

Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node’s descendants. The tree s could also be considered as a subtree of itself.

Example 1:
Given tree s:

     3    / \   4   5  / \ 1   2

Given tree t:
4
/ \
1 2
Return true, because t has the same structure and node values with a subtree of s.
Example 2:
Given tree s:

 3/ \4   5/ \1   2/0

Given tree t:
4
/ \
1 2
Return false.

bool subSub(TreeNode *root1, TreeNode *root2){    if (root1 == NULL && root2 == NULL)return true;    if (root1 == NULL || root2 == NULL)return false;    if (root1->val == root2->val)return subSub(root1->left, root2->left) && subSub(root1->right, root2->right);    else return false;}bool isSubtree(TreeNode* s, TreeNode* t) {    if (t == NULL)return true;    if (s == NULL)return false;    return subSub(s, t) || isSubtree(s->left, t) || isSubtree(s->right, t);}