solution.md

# 从前序与中序遍历序列构造二叉树

<p>给定一棵树的前序遍历 <code>preorder</code> 与中序遍历  <code>inorder</code>。请构造二叉树并返回其根节点。</p>

<p> </p>

<p><strong>示例 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/tree.jpg" />
<pre>
<strong>Input:</strong> preorder = [3,9,20,15,7], inorder = [9,3,15,20,7]
<strong>Output:</strong> [3,9,20,null,null,15,7]
</pre>

<p><strong>示例 2:</strong></p>

<pre>
<strong>Input:</strong> preorder = [-1], inorder = [-1]
<strong>Output:</strong> [-1]
</pre>

<p> </p>

<p><strong>提示:</strong></p>

<ul>
	<li><code>1 <= preorder.length <= 3000</code></li>
	<li><code>inorder.length == preorder.length</code></li>
	<li><code>-3000 <= preorder[i], inorder[i] <= 3000</code></li>
	<li><code>preorder</code> 和 <code>inorder</code> 均无重复元素</li>
	<li><code>inorder</code> 均出现在 <code>preorder</code></li>
	<li><code>preorder</code> 保证为二叉树的前序遍历序列</li>
	<li><code>inorder</code> 保证为二叉树的中序遍历序列</li>
</ul>

<p>以下错误的选项是？</p>

## aop
### before
```cpp

```
### after
```cpp

```

## 答案
```cpp

```
## 选项

### A
```cpp

```

### B
```cpp

```

### C
```cpp

```