let rotateArray (arr,n) =
  let index = ref 0 in
  let tmp = Array.get arr !index in
    while !index < n-1 do
      arr.(!index) <- arr.(!index+1);
      index := !index+1
    done;
    arr.(!index) <- tmp;
    arr

let rotateList = function
  |[] -> []
  |h::t -> List.append t [h]

let rotateListrec = function
  |[] -> []
  |h::t ->
  let tmp = h in
  let rec rl = function
    |[] -> [tmp]
    |h2::t2 -> h2::rl t2 in
  rl t

let rotateArray2 (arr,n) =
  let tmp = Array.get arr 0 in
  let arr2 = Array.init (Array.length arr) (fun _ -> 0) in
  Array.blit arr 1 arr2 0 (n-1);
  arr2.(n-1) <- tmp;
  arr2
type recordl = {fst : int; toshift : int list}
let part1List lst = { fst = List.hd lst; toshift = List.tl lst}
let part2List x = x
let part3List t h = List.append t [h]

let rotateListParts lst = match lst with
  |[] -> []
  |lst ->
  let record = part1List lst in
    part3List (part2List record.toshift) record.fst

type recorda = {fst : int; toshift : int array * int}
let part1Array (arr,n) = { fst = Array.get arr 0; toshift = (arr,n)}
let part2Array (arr,n) =
  let arr2 = Array.init (Array.length arr) (fun _ -> 0) in
  Array.blit arr 1 arr2 0 (n-1);
  (arr2,n)
let part3Array (arr,n) tmp = arr.(n-1) <- tmp; arr

let rotateArrayParts (arr,n) = let record = part1Array (arr,n) in part3Array (part2Array (record.toshift)) record.fst
;;
assert (rotateArray ((Array.init 20 (function _ -> 0)), 3) = Array.init 20 (function _ -> 0));;
assert (rotateArray ((Array.init 20 (function 0 -> 5 | 1 -> 4 | 2 -> 3 | _ -> 0)), 3) = Array.init 20 (function 0 -> 4 | 1 -> 3 | 2 -> 5 | _ -> 0));;
assert (rotateArray2 ((Array.init 20 (function _ -> 0)), 3) = Array.init 20 (function _ -> 0));;
assert (rotateArray2 ((Array.init 20 (function 0 -> 5 | 1 -> 4 | 2 -> 3 | _ -> 0)), 3) = Array.init 20 (function 0 -> 4 | 1 -> 3 | 2 -> 5 | _ -> 0));;
assert (rotateArrayParts ((Array.init 20 (function _ -> 0)), 3) = Array.init 20 (function _ -> 0));;
assert (rotateArrayParts ((Array.init 20 (function 0 -> 5 | 1 -> 4 | 2 -> 3 | _ -> 0)), 3) = Array.init 20 (function 0 -> 4 | 1 -> 3 | 2 -> 5 | _ -> 0));;
assert (rotateList [] = []);;
assert (rotateList [5;4;3] = [4;3;5]);;
assert (rotateListrec [] = []);;
assert (rotateListrec [5;4;3] = [4;3;5]);;
assert (rotateListParts [] = []);;
assert (rotateListParts [5;4;3] = [4;3;5]);;