LeetCode 100. 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&&q!=NULL)
            return false;
        if(p!=NULL&&q==NULL)
            return false;
        
        if(p==NULL&&q==NULL)
            return true;
        
        if(p->val!=q->val)
            return false;
        
       
        
        bool left = isSameTree(p->left,q->left);
        if(!left)
            return false;
        
        bool right = isSameTree(p->right,q->right);
        if(!right)
            return false;
        
        return true;
        
    }
};