1008. Construct Binary Search Tree from Preorder Traversal

https://leetcode.com/problems/construct-binary-search-tree-from-preorder-traversal

Description

Given an array of integers preorder, which represents the preorder traversal of a BST (i.e., binary search tree), construct the tree and return its root.

It is guaranteed that there is always possible to find a binary search tree with the given requirements for the given test cases.

A binary search tree is a binary tree where for every node, any descendant of Node.left has a value strictly less than Node.val, and any descendant of Node.right has a value strictly greater than Node.val.

A preorder traversal of a binary tree displays the value of the node first, then traverses Node.left, then traverses Node.right.

Example 1:

**Input:** preorder = [8,5,1,7,10,12]
**Output:** [8,5,10,1,7,null,12]

Example 2:

**Input:** preorder = [1,3]
**Output:** [1,null,3]

Constraints:

• 1 <= preorder.length <= 100

• 1 <= preorder[i] <= 108

• All the values of preorder are unique.

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