Leetcode -- Same Tree

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