Data update

Task/Permutations/OCaml/permutations-2.ml

@@ -0,0 +1,15 @@
+let rec permutations l =
+   let n = List.length l in
+   if n = 1 then [l] else
+   let rec sub e = function
+      | [] -> failwith "sub"
+      | h :: t -> if h = e then t else h :: sub e t in
+   let rec aux k =
+      let e = List.nth l k in
+      let subperms = permutations (sub e l) in
+      let t = List.map (fun a -> e::a) subperms in
+      if k < n-1 then List.rev_append t (aux (k+1)) else t in
+   aux 0;;
+
+let print l = List.iter (Printf.printf " %d") l; print_newline() in
+List.iter print (permutations [1;2;3;4])