105. Construct Binary Tree from Preorder and Inorder Travers

from collections import deque

class Solution:
    def helper(self, preorder, inorder):
        if not inorder or not preorder:
            return None

        val = preorder.popleft()
        idx = inorder.index(val)

        root = TreeNode(val)
        root.left = self.helper(preorder, inorder[:idx])
        root.right = self.helper(preorder, inorder[idx+1:])

        return root

    def buildTree(self, preorder: List[int], inorder: List[int]) -> TreeNode:
        if not inorder or not preorder:
            return None

        preorder = deque(preorder)

        res = self.helper(preorder, inorder)

        return res