Construct Tree from Inorder and Postorder Traversal

Given two integer arrays inorder and postorder where inorder is the inorder traversal of a binary tree and postorder is the postorder traversal of the same tree, construct and return the binary tree.

Class TreeNode:
    val (int)
    left (TreeNode)
    right (TreeNode)

Input format:

First Parameter - number n1

Second Parameter -Array of numbers inorder of size n1

Third Parameter - number n2

Fourth Parameter - Array of numbers postorder of size n2

Output format:

Return the TreeNode

Example 1:

Input:
    inorder = [9 3 15 20 7]
    postorder = [9 15 7 20 3]
Output: 
    [3 9 20 null null 15 7]

Example 2:

Input:
    inorder = [-25]
    postorder = [-25]
Output:
    [-25]

Constraints:

• 1 <= inorder.length <= 3000
• postorder.length == inorder.length
• -3000 <= inorder[i], postorder[i] <= 3000
• inorder and postorder consist of unique values.
• Each value of postorder also appears in inorder.
• inorder is guaranteed to be the inorder traversal of the tree.
• postorder is guaranteed to be the postorder traversal of the tree.
• Expected Time Complexity: O(N)
• Expected Space Complexity: O(N)