Given two binary trees, write a function to check if they are equal or not.

Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

代码如下：

 1 /**
 2  * Definition for a binary tree node.
 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         if(p==null&&q==null)
13         return true;
14         if(p!=null&&q!=null)
15         {
16             if(p.val==q.val&&isSameTree(p.left,q.left)&&isSameTree(p.right,q.right))
17             return true;
18         }
19         return false;
20     }
21 }