tasks a-s

Task/Semordnilap/OCaml/semordnilap.ocaml

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+module StrSet = Set.Make(String)
+
+let str_rev s =
+  let len = String.length s in
+  let r = String.create len in
+  for i = 0 to len - 1 do
+    r.[i] <- s.[len - 1 - i]
+  done;
+  (r)
+
+let input_line_opt ic =
+  try Some (input_line ic)
+  with End_of_file -> close_in ic; None
+
+let () =
+  let ic = open_in "unixdict.txt" in
+  let rec aux set acc =
+    match input_line_opt ic with
+    | Some word ->
+        let rev = str_rev word in
+        if StrSet.mem rev set
+        then aux set ((word, rev) :: acc)
+        else aux (StrSet.add word set) acc
+    | None ->
+        (acc)
+  in
+  let pairs = aux StrSet.empty [] in
+  let len = List.length pairs in
+  Printf.printf "Semordnilap pairs: %d\n" len;
+  Random.self_init ();
+  for i = 1 to 5 do
+    let (word, rev) = List.nth pairs (Random.int len) in
+    Printf.printf " %s %s\n" word rev
+  done