tests for a and b

ex6_recursion.py

@@ -0,0 +1,49 @@
+# Aufgabe 6: Rekursion
+from dataclasses import dataclass
+from typing import Optional
+
+
+@dataclass
+class Node[T]:
+    mark: T
+    left: Optional["Node[T]"] = None
+    right: Optional["Node[T]"] = None
+
+
+type BTree[T] = Optional[Node[T]]
+
+
+# a)
+def sum_of_subtree(tree: BTree[int]) -> int:
+    match tree:
+        case None:
+            return 0
+        case Node(_, left, right):
+            tree.mark += sum_of_subtree(left) + sum_of_subtree(right)
+            return tree.mark
+
+
+# b)
+def cut_at[T](tree: BTree[T], at: T) -> BTree[T]:
+    match tree:
+        case None:
+            return None
+        case Node(mark, _, _) if mark == at:
+            return None
+        case Node(mark, left, right):  # f(mark)
+            return Node(mark, cut_at(left, at), cut_at(right, at))
+
+
+if __name__ == "__main__":
+    t1 = None
+    assert sum_of_subtree(t1) == 0
+    assert t1 is None
+
+    t3 = Node(1, Node(2, Node(3), Node(4)), Node(5, Node(6)))
+    assert sum_of_subtree(t3) == 21
+    assert t3 == Node(21, Node(9, Node(3), Node(4)), Node(11, Node(6)))
+
+    assert cut_at(None, 42) is None
+    t = Node(1, Node(2, Node(3), Node(4)), Node(3, Node(3), Node(6)))
+    assert cut_at(t, 1) is None
+    assert cut_at(t, 3) == Node(1, Node(2, None, Node(4)))