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 true;
        if(p == NULL && q != NULL)
            return false;
        if(p != NULL && q == NULL)
            return false;

        //establish a recursive relation 
        if(p->val != q->val)
            return false;
        return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
    }
};