Construct Binary Tree from Preorder and Inorder Traversal LeetCode solution in Python

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# Runtime: 274 ms (Top 36.07%) | Memory: 88.6 MB (Top 22.22%)
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# Definition for a binary tree node.
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# class TreeNode(object):
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution(object):
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    def buildTree(self, preorder, inorder):
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        """
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        :type preorder: List[int]
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        :type inorder: List[int]
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        :rtype: TreeNode
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        """
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        if not preorder or not inorder:
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            return None
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        root = TreeNode(preorder[0])
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        mid = inorder.index(preorder[0])
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        root.left = self.buildTree(preorder[1 : mid + 1], inorder[:mid])
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        root.right = self.buildTree(preorder[mid + 1 :], inorder[mid + 1 :])
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        return root