Same Tree

/**
 * Definition for a binary tree node.
 * 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) return q==NULL;
    if(q==NULL) return p==NULL;
    
    if(p->left==NULL && p->right ==NULL){
         {if(q->left==NULL && q->right ==NULL)
             return q->val == p->val;
         }return false;
    }
    
    if(q->left==NULL && q->right ==NULL){
         {if(p->left==NULL && p->right ==NULL)
             return q->val == p->val;
         }return false;
    }
    
    if(!isSameTree(p->left, q->left)) return false; 
    if(!isSameTree(p->right, q->right)) return false;  
    if(p->val != q->val) return false;    //注意，思维的严谨性
    return true;
    }
    
};