/**
 * Definition for a binary tree node.
 * struct TreeNode {
 * int val;
 * TreeNode *left;
 * TreeNode *right;
 * TreeNode() : val(0), left(nullptr), right(nullptr) {}
 * TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
 bool isSameTree(TreeNode* p, TreeNode* q) {
 if (p == NULL && q == NULL)
 return true;
 else if (p == NULL && q != NULL)
 return false;
 else if (p != NULL && q == NULL)
 return false;

 if (p->val != q->val)
 return false;

 return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
 } 
};