day 2

day2.ml

@@ -0,0 +1,41 @@
+let parse_line' f str = Scanf.sscanf str "%d - %d %c : %s%!" f
+
+
+type part1 = {min: int; max: int; char: char; pass: string}
+
+let parse_line1 = parse_line'
+  (fun min max char pass -> {min; max; char; pass})
+
+let count c str =
+  let res = ref 0 in
+  String.iter (fun d -> if c = d then incr res) str;
+  !res
+
+let ok1 {min; max; char; pass} =
+  let res = count char pass in
+  res >= min && res <= max
+
+
+type part2 = {pos1: int; pos2: int; char: char; pass: string}
+
+let parse_line2 = parse_line'
+  (fun pos1 pos2 char pass -> {pos1 = pos1 - 1; pos2 = pos2 - 1; char; pass})
+
+let ok2 {pos1; pos2; char; pass} =
+  (pass.[pos1] = char) <> (pass.[pos2] = char)
+
+
+let main' ~line ~ok input =
+  let count_all = ref 0 in
+  let count_ok = ref 0 in
+  let check l = incr count_all; if ok l then incr count_ok in
+  Bracket.infile_iter_lines input ~line ~iter:check;
+  Printf.printf "%d out of %d ok\n" !count_ok !count_all
+
+let main1 = main' ~line:parse_line1 ~ok:ok1
+let main2 = main' ~line:parse_line2 ~ok:ok2
+let mains = [|main1; main2|]
+
+let main = function
+  | [part; input] -> mains.(int_of_string part - 1) input
+  | _ -> Usage.exit "2 <part> <infile>"