day 12

day12.1.ml

@@ -0,0 +1,91 @@
+(* Common util. Should probably put this in a module or something.. *)
+let get_one_line file =
+  try Some (input_line file) with
+    End_of_file -> None
+
+let get_lines file =
+  let rec input lines =
+    match get_one_line file with
+      Some line -> input (line :: lines)
+    | None -> List.rev lines
+  in input []
+
+let read_file file =
+  let channel = open_in(file) in
+  get_lines channel
+
+let explode s = (* convert a string to a list of chars *)
+  let rec exp i l =
+   if i < 0 then l else exp (i - 1) (s.[i] :: l) in
+  exp (String.length s - 1) [];;
+
+let implode l = String.of_seq (List.to_seq l)
+
+let (<<) f g x = f(g(x))
+let (>>) f g x = g(f(x))
+
+let rec find_idx x = function (* find index of x *)
+  | [] -> raise (Failure "Not Found")
+  | h :: t -> if x = h then 0 else 1 + find_idx x t
+
+let abs x = if x < 0 then -x else x
+
+(* --- *)
+
+(*
+type dir = North | Eath | South | West
+let string_of_dir = function | North -> 'N' | Eeast -> 'E' | South -> 'S' | West -> 'W'
+
+type action = N | E | S | W | L | R | F
+let action_of_char = function | 'N' -> N | 'E' -> E | 'S' -> S | 'W' -> W | 'L' -> L | 'R' -> R | 'F' -> F
+
+type position = int * int
+type bearing = { position: position; heading: char }
+
+(* nah fuck all that *)
+*)
+
+type instruction = { action: char; value: int }
+
+let dirs = [('N', (0, 1)); ('E', (1, 0)); ('S', (0, -1)); ('W', (-1, 0))]
+let dir_list = ['N'; 'E'; 'S'; 'W']
+
+let parse_line = (* from string to instruction *)
+  explode >> function | action :: value -> { action; value = int_of_string @@ implode value }
+
+let rec turn direction heading = function (* returns new heading, matching on degrees *)
+  | 0 -> heading (* doing this 90 degrees at a time *)
+  | d -> (* rotate through our dir_list *)
+      let old_idx = find_idx heading dir_list in
+      let idx_dx = match direction with | 'L' -> -1 | 'R' -> 1 in
+      let new_idx = (old_idx + 4 + idx_dx) mod 4 in (* if we fall off the dir_list in either way, wrap around with mod *)
+      let new_heading = List.nth dir_list new_idx in
+      (* Printf.printf "turning! old_idx %i idx_dx %i new_idx %i new_heading %c" old_idx idx_dx new_idx new_heading; *)
+      turn direction new_heading (d - 90)
+
+let move { action; value } (x, y) heading = (* returns (new location, new heading) *)
+  Printf.printf "@ (%i, %i) facing %c. moving %c %i\n" x y heading action value;
+  match action with
+    | 'L' -> ((x, y), turn 'L' heading value)
+    | 'R' -> ((x, y), turn 'R' heading value)
+    | 'F' ->
+        let (dx, dy) = List.assoc heading dirs in
+        ((x + (dx * value), y + (dy * value)), heading)
+    | dir -> (* Either N, E, S, or W. Find the (dx, dy) and apply it *)
+        let (dx, dy) = List.assoc dir dirs in
+        ((x + (dx * value), y + (dy * value)), heading)
+
+let rec travel (x, y) heading map =
+  match map with
+  | [] -> (x, y)
+  | line :: rest ->
+      let (new_position, new_heading) = move line (x, y) heading in
+      travel new_position new_heading rest
+
+let manhattan (x, y) = (abs x) + abs y
+
+let () =
+  let map = read_file "day12.txt" |> List.map parse_line in
+
+  let (x, y) = map |> travel (0, 0) 'E' in
+  Printf.printf "ending location (%i, %i). manhattan distance: %i\n" x y (manhattan (x, y));

day12.2.ml

@@ -0,0 +1,74 @@
+(* Common util. Should probably put this in a module or something.. *)
+let get_one_line file =
+  try Some (input_line file) with
+    End_of_file -> None
+
+let get_lines file =
+  let rec input lines =
+    match get_one_line file with
+      Some line -> input (line :: lines)
+    | None -> List.rev lines
+  in input []
+
+let read_file file =
+  let channel = open_in(file) in
+  get_lines channel
+
+let explode s = (* convert a string to a list of chars *)
+  let rec exp i l =
+   if i < 0 then l else exp (i - 1) (s.[i] :: l) in
+  exp (String.length s - 1) [];;
+
+let implode l = String.of_seq (List.to_seq l)
+
+let (<<) f g x = f(g(x))
+let (>>) f g x = g(f(x))
+
+let rec find_idx x = function (* find index of x *)
+  | [] -> raise (Failure "Not Found")
+  | h :: t -> if x = h then 0 else 1 + find_idx x t
+
+let abs x = if x < 0 then -x else x
+
+(* --- *)
+
+type instruction = { action: char; value: int }
+
+let dirs = [('N', (0, 1)); ('E', (1, 0)); ('S', (0, -1)); ('W', (-1, 0))]
+let dir_list = ['N'; 'E'; 'S'; 'W']
+
+let parse_line = (* from string to instruction *)
+  explode >> function | action :: value -> { action; value = int_of_string @@ implode value }
+
+let rec turn direction (wx, wy) = function (* returns new waypoint location *)
+  | 0 -> (wx, wy) (* doing this 90 degrees at a time *)
+  | degrees ->
+      let new_position = match direction with
+        | 'L' -> (-1 * wy, wx)
+        | 'R' -> (wy, -1 * wx)
+      in turn direction new_position (degrees - 90)
+
+let move { action; value } (x, y) (wx, wy) = (* returns (new ship location, new waypoint location) *)
+  Printf.printf "@ (%i, %i). moving %c %i\n" x y action value;
+  match action with
+    | 'L' -> ((x, y), turn 'L' (wx, wy) value)
+    | 'R' -> ((x, y), turn 'R' (wx, wy) value)
+    | 'F' -> ((x + (wx * value), y + (wy * value)), (wx, wy))
+    | dir -> (* Either N, E, S, or W. Find the (dx, dy) and apply it *)
+        let (dx, dy) = List.assoc dir dirs in
+        ((x, y), (wx + (dx * value), wy + (dy * value)))
+
+let rec travel (x, y) (wx, wy) map =
+  match map with
+  | [] -> (x, y)
+  | line :: rest ->
+      let (new_position, waypoint_position) = move line (x, y) (wx, wy) in
+      travel new_position waypoint_position rest
+
+let manhattan (x, y) = (abs x) + abs y
+
+let () =
+  let map = read_file "day12.txt" |> List.map parse_line in
+
+  let (x, y) = map |> travel (0, 0) (10, 1) in
+  Printf.printf "ending location (%i, %i). manhattan distance: %i\n" x y (manhattan (x, y));