tasks a-s

Task/Same-Fringe/OCaml/same-fringe.ocaml

@@ -0,0 +1,23 @@
+type 'a btree = Leaf of 'a | BTree of ('a btree * 'a btree)
+
+let rec next = function
+  | [] -> None
+  | h :: t -> match h with
+    | Leaf x -> Some (x,t)
+    | BTree(a,b) -> next (a::b::t)
+
+let samefringe t1 t2 =
+  let rec aux s1 s2 = match (next s1, next s2) with
+    | None, None -> true
+    | None, _ | _, None -> false
+    | Some(a,b), Some(c,d) -> (a=c) && aux b d in
+  aux [t1] [t2]
+
+(* Test: *)
+let () =
+  let u = BTree(Leaf 1, BTree(Leaf 2, Leaf 3)) in
+  let v = BTree(BTree(Leaf 1, Leaf 2), Leaf 3) in
+  let w = BTree(BTree(Leaf 3, Leaf 2), Leaf 1) in
+  let check a b =
+    print_endline (if samefringe a b then "same" else "different") in
+  check u v; check v u; check v w;