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# \[100]\[简单]\[DFS]\[递归] 相同的树

## 题目描述

[100. 相同的树](https://leetcode-cn.com/problems/same-tree/)

给定两个二叉树，编写一个函数来检验它们是否相同。

如果两个树在结构上相同，并且节点具有相同的值，则认为它们是相同的。

示例 1:

```
输入:       1         1
          / \       / \
         2   3     2   3

        [1,2,3],   [1,2,3]

输出: true
```

示例 2:

```
输入:      1          1
          /           \
         2             2

        [1,2],     [1,null,2]

输出: false
```

示例 3:

```
输入:       1         1
          / \       / \
         2   1     1   2

        [1,2,1],   [1,1,2]

输出: false
```

## 解题思路

两棵树从根节点开始, 按照同样的方法(DFS较为简单)迭代判断:

* 当前两个结点相等
* 当前两个结点各自的左右子树相同

根据第二条判断条件去递归判断, 根据第一个条件设置停止点.

```python
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:
        if p is None and q is None:
            return True
        if (p is None and q is not None) or (p is not None and q is None):
            return False
        if p.val != q.val:
            return False

        return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)
```