leetcode第49题（same-tree）

题目：

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. 

思路：

递归判断左子树和右子树的值相不相等就行。

代码：

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