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.
题目：给定两个二叉树，判断他们是不是相等，相等的定义是结构以及各个节点的值都相同
思路：不得不说，二叉树在leetcode上几乎都可以用递归求解，这个是有它的机构觉得，如我之前博文里的求二叉树的深度，反转二叉树，这道题也不例外，注意情况的判断处理,递归求解的代码如下：
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public boolean isSameTree(TreeNode p, TreeNode q) {
if(p == null && q !=null) return false;
if(q == null && p!=null) return false;
if(q == null && q == null) return true;
if(p.val == q.val) {
return isSameTree(p.left,q.left) && isSameTree(p.right,q.right);
}else{
return false;
}
}