/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public boolean isSameTree(TreeNode p, TreeNode q) {
if(p==null&&q==null) return true;
if((p==null&&q!=null)||(p!=null&&q==null)) return false;
if(p.val!=q.val) return false;
else return isSameTree(p.left,q.left)&&isSameTree(p.right,q.right);
}
}