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Construct BST from Preorder


Problem Description

Given an integer array A with distinct elements, which represents the preorder traversal of a binary search tree,
construct the tree and return its root.

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.



**Problem Constraints**
1 <= |A| <= 105
1 <= A.val <= 109
The given array is a valid preorder traversal of a BST.


**Input Format**
The first argument is an integer array denoting the preorder traversal.


**Output Format**
Return the root of the Binary Search Tree.


**Example Input**
Input 1:

A = [2, 1, 4, 3, 5]

Input 2:

A = [1, 2, 3]



**Example Output**
Output 1:

    2
   / \
  1   4
     / \
    3   5

Output 2:

      1
     /
    2
   /
  3



**Example Explanation**
Explanation 1:

We can see that is the tree created by the given pre order traversal.

Explanation 2:

We can see that is the tree created by the given pre order traversal.



NOTE: You only need to implement the given function. Do not read input, instead use the arguments to the function. Do not print the output, instead return values as specified. Still have a question? Checkout Sample Codes for more details.
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