commit

lib/foobar.ml

@@ -0,0 +1,46 @@
+type match' =
+  string (* home team *) * int (* goal difference *) * string (* away team *)
+
+let matches =
+  [
+    ("foo", 1, "car");
+    ("foo", 0, "bar");
+    ("foo", 1, "far");
+    ("car", 1, "bar");
+    ("foo", ~-1, "bar");
+    ("tar", 1, "fir");
+    ("bar", 1, "qux");
+    ("jor", ~-1, "far");
+    ("xir", 1, "kar");
+    ("car", ~-1, "qux");
+    ("far", 1, "qux");
+    ("car", 1, "foo");
+  ]
+
+let way a b =
+  let rec aux (at : string) (visited : string list) (accum : match' list) =
+    if at = b then [ List.rev accum ]
+    else
+      let matches =
+        matches |> List.filter (function _, score, _ -> score <> 0)
+      in
+      let h =
+        matches
+        |> List.filter (function home, score, away ->
+               score > 0 && home = at && not (List.exists (( = ) away) visited))
+        |> List.map (function (_, _, away) as x ->
+               aux away (at :: visited) (x :: accum))
+        |> List.concat
+      in
+      let a =
+        matches
+        |> List.filter (function home, score, away ->
+               score < 0 && away = at && not (List.exists (( = ) home) visited))
+        |> List.map (function (home, _, _) as x ->
+               aux home (at :: visited) (x :: accum))
+        |> List.concat
+      in
+      a @ h
+  in
+  aux a [] []
+