leetcode--Same Tree

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.

分类：二叉树

题意：判断两个二叉树是否相同。

解法1：递归。对于两个根节点而已，如果都为空，则相同。如果其中一个为空，另外一个不为空，则返回假。

如果两个都不为空，判断值是否相同。如果相同，递归判断两者的左右子树。

/** * Definition for a binary tree node. * 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;else if(p==null&&q!=null) return false;else if(p!=null&&q==null) return false;else{if(p.val==q.val){return isSameTree(p.left, q.left)&&isSameTree(p.right, q.right);}else{return false;}}    }}