Data commit

Task/Find-the-missing-permutation/OCaml/find-the-missing-permutation-1.ocaml

@@ -0,0 +1,18 @@
+(* insert x at all positions into li and return the list of results *)
+let rec insert x = function
+  | [] -> [[x]]
+  | a::m as li -> (x::li) :: (List.map (fun y -> a::y) (insert x m))
+
+(* list of all permutations of li *)
+let permutations li =
+  List.fold_right (fun a z -> List.concat (List.map (insert a) z)) li [[]]
+
+(* convert a string to a char list *)
+let chars_of_string s =
+  let cl = ref [] in
+  String.iter (fun c -> cl := c :: !cl) s;
+  (List.rev !cl)
+
+(* convert a char list to a string *)
+let string_of_chars cl =
+  String.concat "" (List.map (String.make 1) cl)

Task/Find-the-missing-permutation/OCaml/find-the-missing-permutation-2.ocaml

@@ -0,0 +1,16 @@
+let deficient_perms = [
+  "ABCD";"CABD";"ACDB";"DACB";
+  "BCDA";"ACBD";"ADCB";"CDAB";
+  "DABC";"BCAD";"CADB";"CDBA";
+  "CBAD";"ABDC";"ADBC";"BDCA";
+  "DCBA";"BACD";"BADC";"BDAC";
+  "CBDA";"DBCA";"DCAB";
+  ]
+
+let it = chars_of_string (List.hd deficient_perms)
+
+let perms = List.map string_of_chars (permutations it)
+
+let results = List.filter (fun v -> not(List.mem v deficient_perms)) perms
+
+let () = List.iter print_endline results

Task/Find-the-missing-permutation/OCaml/find-the-missing-permutation-3.ocaml

@@ -0,0 +1,30 @@
+let array_of_perm s =
+	let n = String.length s in
+	Array.init n (fun i -> int_of_char s.[i] - 65);;
+	
+let perm_of_array a =
+	let n = Array.length a in
+	let s = String.create n in
+	Array.iteri (fun i x ->
+		s.[i] <- char_of_int (x + 65)
+	) a;
+	s;;
+
+let find_missing v =
+	let n = String.length (List.hd v) in
+	let a = Array.make_matrix n n 0
+	and r = ref v in
+	List.iter (fun s ->
+		let u = array_of_perm s in
+		Array.iteri (fun i x -> x.(u.(i)) <- x.(u.(i)) + 1) a
+	) v;
+	let q = Array.make n 0 in
+	Array.iteri (fun i x ->
+		Array.iteri (fun j y ->
+			if y mod 2 != 0 then q.(i) <- j
+		) x
+	) a;
+	perm_of_array q;;
+
+find_missing deficient_perms;;
+(* - : string = "DBAC" *)