leetcode 100.Same Tree

题目链接：https://leetcode.com/problems/same-tree/?tab=Description

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.

用深度优先遍历两个二叉树，比较对应节点的值

方法一：

字节一开始写的，最直接的方法

/** * Definition for a binary tree node. * 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 1;        else if((p==NULL&&q!=NULL)||(q==NULL&&p!=NULL))            return 0;        else if(p->val!=q->val)            return 0;        else if(isSameTree(p->left,q->left))            return isSameTree(p->right,q->right);        else            return 0;                }};

方法二：

更简洁的代码

/** * Definition for a binary tree node. * 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) {            return (p==NULL&&q==NULL)||                   ((p!=NULL&&q!=NULL&&p->val==q->val)&&                   isSameTree(p->left,q->left)&&isSameTree(p->right,q->right));//左右子树都得相同    }};