construct-binary-tree-from-preorder-and-inorder-traversal

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Algorithms

Given two integer arrays <code>preorder</code> and <code>inorder</code> where <code>preorder</code> is the preorder traversal of a binary tree and <code>inorder</code> is the inorder traversal of the same tree, construct and return the binary tree.

&nbsp;
Example 1:
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/tree.jpg" style="width: 277px; height: 302px;" />
<pre>
Input: preorder = [3,9,20,15,7], inorder = [9,3,15,20,7]
Output: [3,9,20,null,null,15,7]
</pre>

Example 2:

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

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= preorder.length &lt;= 3000</code></li>
	<li><code>inorder.length == preorder.length</code></li>
	<li><code>-3000 &lt;= preorder[i], inorder[i] &lt;= 3000</code></li>
	<li><code>preorder</code> and <code>inorder</code> consist of unique values.</li>
	<li>Each value of <code>inorder</code> also appears in <code>preorder</code>.</li>
	<li><code>preorder</code> is guaranteed to be the preorder traversal of the tree.</li>
	<li><code>inorder</code> is guaranteed to be the inorder traversal of the tree.</li>
</ul>

buildTree

Construct Binary Tree from Preorder and Inorder Traversal

Construct Binary Tree from Inorder and Postorder Traversal

construct-binary-tree-from-inorder-and-postorder-traversal

从中序与后序遍历序列构造二叉树

Tree

Array

Hash Table

Divide and Conquer

Binary Tree

给定两个整数数组&nbsp;<code>preorder</code> 和 <code>inorder</code>&nbsp;，其中&nbsp;<code>preorder</code> 是二叉树的先序遍历， <code>inorder</code>&nbsp;是同一棵树的中序遍历，请构造二叉树并返回其根节点。

&nbsp;

示例 1:
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/tree.jpg" style="height: 302px; width: 277px;" />
<pre>
输入: preorder = [3,9,20,15,7], inorder = [9,3,15,20,7]
输出: [3,9,20,null,null,15,7]
</pre>

示例 2:

<pre>
输入: preorder = [-1], inorder = [-1]
输出: [-1]
</pre>

&nbsp;

提示:

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