Solutions for Day 2

* Part 1 refactored * Part 2 solved

Author: renormalize

bin/day2bin.ml

@@ -1,7 +1,5 @@
-let option_list =
- List.map Day2.is_valid_game (Day2.input_line_list "day2/input.txt")
-
-let unpack a b = match b with Some x -> a + x | None -> a
-let sum = List.fold_left unpack 0 option_list
 let () = Printf.printf "\nSolving Day 2!\n"
-let () = Printf.printf "The sum of the Game IDs is: %d\n\n" sum
+let sum = Day2.sum_valid_games (Day2.input_line_list "day2/input.txt")
+let () = Printf.printf "The sum of the Game IDs is: %d\n" sum
+let sum_prod = Day2.sum_prod_max (Day2.input_line_list "day2/input.txt")
+let () = Printf.printf "The sum of products of max balls is: %d\n\n" sum_prod

day2/day2.ml

@@ -1,29 +1,76 @@
 let input_line_list file = In_channel.input_lines (In_channel.open_text file)
 
-let validate_trials sets =
- let validate_set set =
- let validate_color s =
- let balls_and_color = String.split_on_char ' ' s in
- let balls, colour =
- (int_of_string (List.nth balls_and_color 0), List.nth balls_and_color 1)
- in
- match colour with
- | "red" -> balls <= 12
- | "green" -> balls <= 13
- | "blue" -> balls <= 14
- | _ -> false
- in
- let ball_list_in_set =
- List.map String.trim (String.split_on_char ',' set)
+type ball = Red of int | Green of int | Blue of int | None
+
+let game_int_and_ball_strings s =
+ let game_and_sets = String.split_on_char ':' s in
+ let game_int = int_of_string (Str.string_after (List.hd game_and_sets) 5) in
+ let ball_strings =
+ List.map String.trim
+ (Str.split (Str.regexp "[;,]") (List.nth game_and_sets 1))
+ in
+ (game_int, ball_strings)
+
+let string_to_ball s =
+ let color_count_split = String.split_on_char ' ' s in
+ let count, color =
+ (List.nth color_count_split 0, List.nth color_count_split 1)
+ in
+ match color with
+ | "red" -> Red (int_of_string count)
+ | "green" -> Green (int_of_string count)
+ | "blue" -> Blue (int_of_string count)
+ | _ -> None
+
+let validate_ball ball =
+ match ball with
+ | Red r -> if r <= 12 then Red r else None
+ | Green g -> if g <= 13 then Green g else None
+ | Blue b -> if b <= 14 then Blue b else None
+ | None -> None
+
+let sum_valid_games game_list =
+ let validate_game s =
+ let game_int, balls_string = game_int_and_ball_strings s in
+ let ball_list = List.map string_to_ball balls_string in
+ let valid_balls = List.map validate_ball ball_list in
+ let valid_balls_bool =
+ List.map (fun x -> match x with None -> false | _ -> true) valid_balls
  in
- List.fold_left ( && ) true (List.map validate_color ball_list_in_set)
+ if List.fold_left ( && ) true valid_balls_bool then Some game_int else None
+ in
+ let rec sum_valid_games_helper acc game_list_int_option =
+ match game_list_int_option with
+ | [] -> acc
+ | h :: t -> (
+ match h with
+ | Some a -> sum_valid_games_helper (acc + a) t
+ | None -> sum_valid_games_helper acc t)
  in
- List.fold_left ( && ) true
- (List.map validate_set (String.split_on_char ';' sets))
+ sum_valid_games_helper 0 (List.map validate_game game_list)
 
-let is_valid_game s =
- let sets = String.split_on_char ':' s in
- let day, trials =
- (int_of_string (Str.string_after (List.nth sets 0) 5), List.nth sets 1)
+let sum_prod_max list =
+ let max_each_color s =
+ let _, balls_string = game_int_and_ball_strings s in
+ let ball_list = List.map string_to_ball balls_string in
+ let rec max_balls red green blue valid_balls =
+ match valid_balls with
+ | [] -> (red, green, blue)
+ | Red r :: t ->
+ if red < r then max_balls r green blue t
+ else max_balls red green blue t
+ | Blue b :: t ->
+ if blue < b then max_balls red green b t
+ else max_balls red green blue t
+ | Green g :: t ->
+ if green < g then max_balls red g blue t
+ else max_balls red green blue t
+ | None :: t -> max_balls red green blue t
+ in
+ max_balls 0 0 0 ball_list
+ in
+ let prod_max s =
+ let r, g, b = max_each_color s in
+ r * g * b
  in
- match validate_trials trials with true -> Some day | false -> None
+ List.fold_left ( + ) 0 (List.map prod_max list)