Same Tree

simple recursion problem
 1 /**
 2  * Definition for binary tree
 3  * public class TreeNode {
 4  *     int val;
 5  *     TreeNode left;
 6  *     TreeNode right;
 7  *     TreeNode(int x) { val = x; }
 8  * }
 9  */
10 public class Solution {
11     public boolean isSameTree(TreeNode p, TreeNode q) {
12         // IMPORTANT: Please reset any member data you declared, as
13         // the same Solution instance will be reused for each test case.
14         if(p == null && q == null)
15             return true;
16         if(p == null && q != null)
17             return false;
18         if(p!=null && q == null)
19             return false;
20         if(p.val == q.val)
21             return (isSameTree(p.left, q.left))&&(isSameTree(p.right,q.right));
22         else
23             return false;
24         
25     }
26 }