★leetcode★ same-tree

題目要求：

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.

判斷兩棵二叉樹是否相等

解題思路：

遞歸思想（好像大多數關於二叉樹的題目都可以用遞歸來解決）

 1 /**
 2  * Definition for binary tree
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     bool isSameTree(TreeNode *p, TreeNode *q)
13     {
14         if(p == NULL && q == NULL)
15             return true;
16         else if(p == NULL || q == NULL)
17             return false;
18 
19         if(p->val == q->val)
20         {
21             return (isSameTree(p->left, q->left) && (isSameTree(p->right, q->right)));
22         }
23         return false;
24 
25 
26 
27     }
28 };