105. Construct Binary Tree from Preorder and Inorder 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, preorder: List[int], inorder: List[int]) -> TreeNode:
        if (not preorder) or (not inorder):
            return None
        
        # root is start of preorder
        root_val = preorder.pop(0)
        root_index = inorder.index(root_val)
        
        node = TreeNode(root_val)
        node.left = self.buildTree(preorder[:root_index], inorder[0:root_index])
        node.right = self.buildTree(preorder[root_index:], inorder[(root_index + 1):])
        
        return node