Hackerrank Functional Programming Challenge w/ OCaml

a.md

This is a list of my solutions for Functional Programming Challenge in hackerrank and solved with OCaml.

array_of_n_elements.ml

(* returns an array of n elements *)
let make_array n = 
    let rec f xs = function
        | 0 -> xs
        | n -> [n] @ f xs (n - 1)
    in f [] n

let () =
    let n = int_of_string (read_line ()) in
    let arr = make_array n in
    List.iter ( Printf.printf "%d " ) arr

filter.ml

(* Enter your code here. Read input from STDIN. Print output to STDOUT *)
let rec read_lines () =
    try let line = read_line () in
        int_of_string (line) :: read_lines()
    with
        End_of_file -> []

let f n arr = 
   let rec f n = function
        | [] -> []
        | [x] when x < n -> [x] 
        | x::xs -> (if x < n then [x] else []) @ f n xs
    in f n arr 

let () =
    let n::arr = read_lines() in
    arr 
        |> f n 
        |> List.iter (fun x -> print_int x; print_newline ());;

filter_positions_in_list.ml

let rec read_lines () =
    try let line = read_line () in
        int_of_string (line) :: read_lines()
    with
        End_of_file -> []

let f arr = 
    let rec f n = function
        | [] -> []
        | x::xs -> if n mod 2 == 0  
            then f (n+1) xs 
            else [x] @ f (n+1) xs
    in f 0 arr

let () =
    let arr = read_lines() in
    arr 
    |> f
    |>List.iter (fun x -> print_int x; print_newline ()) ;;

list_replication.ml

let rec read_lines () =
    try let line = read_line () in
        int_of_string (line) :: read_lines()
    with
        End_of_file -> []

let compare a b = if a < b then -1 else 1

let f n arr = 
   let rec f l = function
        | 0 -> l
        | n -> f (arr @ l) (n-1) 
    in
        (f [] n) 
        |> List.sort compare

let () =
    let n::arr = read_lines() in
    let ans = f n arr in
    List.iter (fun x -> print_int x; print_newline ()) ans;;

reverse_a_list.ml

let rec read_lines () =
    try let line = read_line () in
        int_of_string (line) :: read_lines()
    with
        End_of_file -> []

let rev arr = 
   let rec rev = function
        | [] -> []
        | [x] -> [x] 
        | x::xs -> (rev xs) @ [x]
    in
        rev arr

let () =
    let arr = read_lines() in
    arr 
      |> rev
      |> List.iter (fun x -> print_int x; print_newline ());;

update_list.ml

let f arr = 
    let rec f = function
    | [] -> []
    | x::xs -> [ if x < 0 then x * -1 else x ] @ f xs
    in f arr

let rec read_lines () = 
    try let line = read_line () in
        line :: read_lines()
    with
        End_of_file -> []
            
let () =
    let inp = read_lines () in
    let arr = List.map int_of_string inp in
    let result = f arr in
    let output = List.map string_of_int result in
    print_string (String.concat "\n" output) ;;

bisa bisanya pake ocaml

gak ada pilihan lain pak @efi-sre