Add binary search in OCaml (#90)

01_introduction_to_algorithms/ocaml/binary_search.ml

@@ -0,0 +1,25 @@
+let rec binary_search ?(min = 0) ?(max = None) seq target =
+  let max_ = match max with None -> Array.length seq - 1 | Some i -> i in
+  if min > max_ then None
+  else if Array.length seq = 0 then None
+  else
+    let mid = (max_ + min) / 2 in
+    let current = seq.(mid) in
+    if current = target then Some mid
+    else if current > target then
+      binary_search ~min ~max:(Some (mid - 1)) seq target
+    else
+      binary_search ~min:(mid + 1) ~max seq target
+
+let print_result result =
+  match result with
+  | None -> print_endline "not found"
+  | Some i -> print_string "found: " ; print_int i ; print_newline ()
+
+let my_list = [|1; 3; 5; 7; 9|]
+
+(* 1 *)
+let () = print_result (binary_search my_list 3)
+
+(* None *)
+let () = print_result (binary_search my_list (-1))