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|
defmodule Day15 do
defmodule Game do
@derive Inspect
defstruct [:grid, :robot, :moves]
def from_data(data) do
[grid, moves] = data
|> String.split("\n\n", trim: true)
grid = grid
|> String.split("\n", trim: true)
|> Enum.with_index()
|> Enum.flat_map(fn {s, i} ->
String.codepoints(s)
|> Enum.with_index()
|> Enum.map(fn {c, j} -> {{i, j}, c} end)
end)
|> Map.new()
robot = grid
|> Enum.find_value(fn {pos, c} -> c == "@" and pos end)
moves = moves
|> String.split("\n", trim: true)
|> Enum.flat_map(&String.codepoints/1)
%Game{grid: grid, robot: robot, moves: moves}
end
def expand(game) do
grid = game.grid
|> Enum.flat_map(fn {{i, j}, v} ->
case v do
"." -> [{{i, j*2}, "."}, {{i, j*2+1}, "."}]
"@" -> [{{i, j*2}, "@"}, {{i, j*2+1}, "."}]
"O" -> [{{i, j*2}, "["}, {{i, j*2+1}, "]"}]
"#" -> [{{i, j*2}, "#"}, {{i, j*2+1}, "#"}]
end
end)
|> Map.new()
robot = {elem(game.robot, 0), elem(game.robot, 1)*2}
%Game{grid: grid, robot: robot, moves: game.moves}
end
def do_moves(game) do
if game.moves == [] do
game
else
move(game)
|> do_moves()
end
end
defp move(game) do
[move | moves] = game.moves
moved? = check_moves(game.grid, move, game.robot) |> elem(0)
grid =
if moved? do
apply_move(game.grid, move, queue_new(game.robot))
else
game.grid
end
robot = if moved? do next_pos(game.robot, move) else game.robot end
%Game{grid: grid, robot: robot, moves: moves}
end
defp check_moves(grid, move, k, vis \\ MapSet.new()) do
if MapSet.member?(vis, k) do
{true, vis}
else
vis = MapSet.put(vis, k)
v = Map.fetch!(grid, k)
case v do
"." ->
{true, vis}
"#" ->
{false, vis}
"@" ->
check_moves(grid, move, next_pos(k, move), vis)
"O" ->
check_moves(grid, move, next_pos(k, move), vis)
"[" ->
nk = next_pos(k, move)
if move == "^" or move == "v" do
{oi, _} = k
{_, nj} = nk
{a1, vis} = check_moves(grid, move, nk, vis)
{a2, vis} = check_moves(grid, move, {oi, nj+1}, vis)
{a1 and a2, vis}
else
check_moves(grid, move, nk, vis)
end
"]" ->
nk = next_pos(k, move)
if move == "^" or move == "v" do
{oi, _} = k
{_, nj} = nk
{a1, vis} = check_moves(grid, move, nk, vis)
{a2, vis} = check_moves(grid, move, {oi, nj-1}, vis)
{a1 and a2, vis}
else
check_moves(grid, move, nk, vis)
end
end
end
end
defp apply_move(grid, move, queue) do
if queue_empty(queue) do
grid
else
{pos, nv, queue} = queue_pop(queue, move)
v = Map.fetch!(grid, pos)
case v do
"#" ->
raise "Unexpected"
"." ->
apply_move(Map.put(grid, pos, nv), move, queue)
v ->
grid = Map.put(grid, pos, nv)
npos = next_pos(pos, move)
nv = Map.fetch!(grid, npos)
queue =
if (move == "^" or move == "v") and (nv == "[" or nv == "]") do
{i, j} = npos
j = if nv == "[" do j+1 else j-1 end
queue = queue_add(queue, npos, v)
queue_add(queue, {i, j}, ".")
else
queue_add(queue, npos, v)
end
apply_move(grid, move, queue)
end
end
end
defp queue_add(queue, pos, v) do
case :gb_trees.lookup(pos, queue) do
:none ->
:gb_trees.insert(pos, v, queue)
{_, "."} ->
:gb_trees.update(pos, v, queue)
_ ->
queue
end
end
defp queue_pop(queue, move) do
if move == "^" do
:gb_trees.take_largest(queue)
else
:gb_trees.take_smallest(queue)
end
end
defp queue_new(robot) do
:gb_trees.insert(robot, ".", :gb_trees.empty())
end
defp queue_empty(queue) do
:gb_trees.is_empty(queue)
end
defp next_pos({i, j}, move) do
case move do
">" -> {i, j+1}
"^" -> {i-1, j}
"<" -> {i, j-1}
"v" -> {i+1, j}
end
end
def print(game) do
w = game.grid |> Enum.map(fn {{_, j}, _} -> j end) |> Enum.max()
h = game.grid |> Enum.map(fn {{i, _}, _} -> i end) |> Enum.max()
for i <- 0..h do
for j <- 0..w, reduce: [] do
acc -> [Map.fetch!(game.grid, {i, j}) | acc]
end
|> Enum.reverse()
|> Enum.join("")
|> IO.puts()
end
game
end
end
def part1(data) do
data
|> Game.from_data()
|> Game.do_moves()
|> then(& &1.grid)
|> Enum.filter(fn {_, v} -> v == "O" end)
|> Enum.map(fn {{i, j}, _} -> i*100 + j end)
|> Enum.sum()
end
def part2(data) do
data
|> Game.from_data()
|> Game.expand()
|> Game.do_moves()
|> then(& &1.grid)
|> Enum.filter(fn {_, v} -> v == "[" end)
|> Enum.map(fn {{i, j}, _} -> i*100 + j end)
|> Enum.sum()
end
end
data = IO.read(:stdio, :eof)
{time1, ans1} = :timer.tc(fn -> Day15.part1(data) end)
IO.puts("Time : #{time1 / 1000000}")
IO.puts("Answer: #{ans1}")
{time2, ans2} = :timer.tc(fn -> Day15.part2(data) end)
IO.puts("Time : #{time2 / 1000000}")
IO.puts("Answer: #{ans2}")
|
