leetcode笔记：Same Tree

一. 题目描述

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.

二. 题目分析

题目的意思很简单，判断两棵树是否相同，递归，对两棵树的结点进行比较即可。

三. 示例代码

#include <iostream>

using namespace std;

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

class Solution {
public:
    bool isSameTree(TreeNode *p, TreeNode *q) 
    {
        if (p == NULL && q == NULL)
            return true;
        // p和q不同时到达叶节点，则剪枝
        else if ((p != NULL && q == NULL) || (p == NULL && q != NULL))
            return false;
        return (p->val == q->val) && isSameTree(p->left, q->left)
               && isSameTree(p->right, q->right);
    }
};

四. 小结

该题属于二叉树的遍历中的基础题目，难度不大。