105.construct binary tree from preorder and inorder traversal

[xbam326]

解いた問題：https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/description/
次に解く問題：https://leetcode.com/problems/paint-fence/description/

[nodchip]

最初に preorder/inorder が空かどうかをチェックすることで、少しシンプルにできそうです。

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

        root_val = preorder[0]
        root = TreeNode(preorder[0])
        root_index_at_inorder = inorder.index(root_val)

        root.left = self.buildTree(
            preorder[1 : root_index_at_inorder + 1],
            inorder[:root_index_at_inorder],
        )

        root.right = self.buildTree(
            preorder[root_index_at_inorder + 1 :],
            inorder[root_index_at_inorder + 1 :],
        )

        return root