Cheating with binary tree goop

leetcode/stuff.py

@@ -319,3 +319,34 @@ def binary_tree_from_list(inlist: list[int | None]) -> stdlib.BinaryTreeNode | N
             node.right = nodes_copy.pop()
 
     return root
+
+
+def binary_tree_from_preorder_inorder(
+    preorder: list[int], inorder: list[int]
+) -> stdlib.BinaryTreeNode | None:
+    preorder_reversed = preorder[::-1]
+
+    def subtree(left: list[int], right: list[int]) -> stdlib.BinaryTreeNode:
+        root: stdlib.BinaryTreeNode = typing.cast(
+            stdlib.BinaryTreeNode, stdlib.TreeNode(preorder_reversed.pop())
+        )
+
+        if len(left) > 1:
+            split_pos = left.index(preorder_reversed[-1])
+            root.left = subtree(left[:split_pos], left[split_pos + 1 :])
+        elif len(left) == 1:
+            preorder_reversed.remove(left[0])
+            root.left = typing.cast(stdlib.BinaryTreeNode, stdlib.TreeNode(left[0]))
+
+        if len(right) > 1:
+            split_pos = right.index(preorder_reversed[-1])
+            root.right = subtree(right[:split_pos], right[split_pos + 1 :])
+        elif len(right) == 1:
+            preorder_reversed.remove(right[0])
+            root.right = typing.cast(stdlib.BinaryTreeNode, stdlib.TreeNode(right[0]))
+
+        return root
+
+    split_pos = inorder.index(preorder[0])
+
+    return subtree(inorder[:split_pos], inorder[split_pos + 1 :])