106. Construct Binary Tree From Inorder and Postorder Traversal

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def buildTree(self, inorder: List[int], postorder: List[int]) -> TreeNode:
        if (not inorder) or (not postorder):
            return None
        
        # root is end of postorder
        root_val = postorder.pop()
        root_index = inorder.index(root_val)

        node = TreeNode(root_val)
        node.left = self.buildTree(inorder[0:root_index], postorder[:root_index])
        node.right = self.buildTree(inorder[(root_index + 1):], postorder[root_index:])

        return node