Add Binary Search in OCaml

archive/o/ocaml/binary-search.ml

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+let ( let* ) = Option.bind
+let ( let+ ) f g = Option.map g f
+
+let binary_search target arr =
+  let rec aux lo hi =
+    if lo >= hi then false
+    else
+      let mid = lo + ((hi - lo) / 2) in
+      if target = arr.(mid) then true
+      else if target < arr.(mid) then aux lo mid
+      else aux (mid + 1) hi
+  in
+  aux 0 (Array.length arr)
+
+let rec is_sorted = function
+  | [] | [ _ ] -> true
+  | a :: (b :: _ as rest) -> a <= b && is_sorted rest
+
+let parse_list list_str =
+  let rec aux acc l =
+    match l with
+    | [] -> Some (List.rev acc)
+    | head :: rest ->
+        let* num = head |> String.trim |> int_of_string_opt in
+        aux (num :: acc) rest
+  in
+  list_str |> String.split_on_char ',' |> aux []
+
+let parse_args argv =
+  match argv with
+  | [| _; nums; key |] ->
+      let* parsed_nums = parse_list nums in
+      let+ parsed_key = int_of_string_opt key in
+      (parsed_nums, parsed_key)
+  | _ -> None
+
+let () =
+  match parse_args Sys.argv with
+  | Some (nums, key) when is_sorted nums ->
+      Printf.printf "%b\n" (binary_search key (Array.of_list nums))
+  | _ ->
+      print_endline
+        {|Usage: please provide a list of sorted integers ("1, 4, 5, 11, 12") and the integer to find ("11")|}