day 17 yo

day17.1.ml

@@ -0,0 +1,94 @@
+(* Common util. Should probably put this in a module or something.. *)
+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 uniq = function (* dedups a list *)
+  | [] -> []
+  | x :: xs ->
+      if List.mem x xs
+      then uniq xs
+      else x :: (uniq xs)
+
+(* --- *)
+
+let string_of_cube (x, y, z) = Printf.sprintf "(%i, %i, %i) " x y z
+let print_cube = print_string << string_of_cube
+let print_cubes cubes = (List.map print_cube cubes; print_newline ())
+
+let read_grid lines = (* string list to active cube list *)
+  List.mapi (fun x line ->
+    List.mapi (fun y cell ->
+      if cell = '#' then Some (x, y, 0) else None
+    ) (explode line)
+  ) lines
+  |> List.concat
+  |> List.filter Option.is_some
+  |> List.map Option.get
+
+let neighbor_d = [-1; 0; 1]
+
+let find_neighbors (x, y, z) = (* find all of the neighboring cubes *)
+  List.map (fun dx ->
+    List.map (fun dy ->
+      List.map (fun dz ->
+        (x + dx, y + dy, z + dz)
+      ) neighbor_d
+    ) neighbor_d
+  ) neighbor_d
+  |> List.concat |> List.concat (* flatten *)
+  |> List.filter (fun (x', y', z') -> not (x = x' && y = y' && z = z')) (* remove the point itself *)
+
+let update position cubes = (* returns true if this position should be active *)
+  let neighbors = find_neighbors position in
+  let active_neighbors = List.filter (fun x -> List.mem x cubes) neighbors in
+  let num_active_neighbors = List.length active_neighbors in
+  let active = List.mem position cubes in
+  let active' = num_active_neighbors = 3 || (active && num_active_neighbors = 2) in
+  num_active_neighbors = 3 || (active && num_active_neighbors = 2)
+
+let cycle cubes =
+  let neighbors = List.map find_neighbors cubes |> List.concat in
+  let uniq_neighbors = uniq neighbors in
+  let cubes' = List.map (fun n -> (n, update n cubes)) uniq_neighbors in
+  (* List.filter (fun (c, active) -> active) cubes' (* only return the active ones *) *)
+  List.filter_map (fun (c, active) -> if active then Some c else None) cubes' (* only return the active ones *)
+
+let rec go cubes = function (* cycle n times *)
+  | 0 -> cubes
+  | n -> go (cycle cubes) (n - 1)
+
+let () =
+  let test = [
+    ".#.";
+    "..#";
+    "###";
+  ] in
+
+  let start = [
+    "...###.#";
+    "#.#.##..";
+    ".##.##..";
+    "..##...#";
+    ".###.##.";
+    ".#..##..";
+    ".....###";
+    ".####..#";
+  ] in
+
+  let cubes = read_grid start in
+  print_string "starting coordinates\n";
+  print_cubes cubes;
+  print_newline ();
+
+  let n = 6 in
+  let cubes' = go cubes n in
+  Printf.printf "after %i cycle(s)\n" n;
+  print_cubes cubes';
+  Printf.printf "count: %i\n" (List.length cubes');

day17.2.ml

@@ -0,0 +1,99 @@
+(* Common util. Should probably put this in a module or something.. *)
+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 uniq = function (* dedups a list *)
+  | [] -> []
+  | x :: xs ->
+      if List.mem x xs
+      then uniq xs
+      else x :: (uniq xs)
+
+(* --- *)
+
+let string_of_cube (x, y, z, w) = Printf.sprintf "(%i, %i, %i, %i) " x y z w
+let print_cube = print_string << string_of_cube
+let print_cubes cubes = (List.map print_cube cubes; print_newline ())
+
+let read_grid lines = (* string list to active cube list *)
+  List.mapi (fun x line ->
+    List.mapi (fun y cell ->
+      if cell = '#' then Some (x, y, 0, 0) else None
+    ) (explode line)
+  ) lines
+  |> List.concat
+  |> List.filter Option.is_some
+  |> List.map Option.get
+
+let neighbor_d = [-1; 0; 1]
+
+(* donno how to do this nicely.. *)
+let find_neighbors (x, y, z, w) = (* find all of the neighboring cubes *)
+  List.map (fun dx ->
+    List.map (fun dy ->
+      List.map (fun dz ->
+        List.map (fun dw ->
+          (x + dx, y + dy, z + dz, w + dw)
+        ) neighbor_d
+      ) neighbor_d
+    ) neighbor_d
+  ) neighbor_d
+  |> List.concat |> List.concat |> List.concat (* flatten *)
+  |> List.filter (fun (x', y', z', w') -> not (x = x' && y = y' && z = z' && w = w')) (* remove the point itself *)
+
+let update position cubes = (* returns true if this position should be active *)
+  let neighbors = find_neighbors position in
+  let active_neighbors = List.filter (fun x -> List.mem x cubes) neighbors in
+  let num_active_neighbors = List.length active_neighbors in
+  let active = List.mem position cubes in
+  let active' = num_active_neighbors = 3 || (active && num_active_neighbors = 2) in
+  num_active_neighbors = 3 || (active && num_active_neighbors = 2)
+
+let cycle cubes =
+  let neighbors = List.map find_neighbors cubes |> List.concat in
+  let uniq_neighbors = uniq neighbors in
+  let cubes' = List.map (fun n -> (n, update n cubes)) uniq_neighbors in
+  List.filter_map (fun (c, active) -> if active then Some c else None) cubes' (* only return the active ones *)
+
+let rec go cubes n = (* cycle n times *)
+  Printf.printf "GO! %i\n" n;
+  match n with
+  | 0 -> cubes
+  | n -> go (cycle cubes) (n - 1)
+
+let () =
+  let test = [
+    ".#.";
+    "..#";
+    "###";
+  ] in
+
+  let start = [
+    "...###.#";
+    "#.#.##..";
+    ".##.##..";
+    "..##...#";
+    ".###.##.";
+    ".#..##..";
+    ".....###";
+    ".####..#";
+  ] in
+
+  let cubes = read_grid start in
+  print_string "starting coordinates\n";
+  print_cubes cubes;
+  print_newline ();
+
+  let n = 6 in
+  let cubes' = go cubes n in
+  Printf.printf "after %i cycle(s)\n" n;
+  print_cubes cubes';
+  let count = List.length cubes' in
+  Printf.printf "count: %i\n" count;