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# Day 13
```elixir
Mix.install([
{:kino, "~> 0.14.2"},
{:kino_aoc, "~> 0.1.7"},
{:tucan, "~> 0.4.1"},
{:kino_vega_lite, "~> 0.1.13"}
])
```
## Part 1
```elixir
example = """
p=0,4 v=3,-3
p=6,3 v=-1,-3
p=10,3 v=-1,2
p=2,0 v=2,-1
p=0,0 v=1,3
p=3,0 v=-2,-2
p=7,6 v=-1,-3
p=3,0 v=-1,-2
p=9,3 v=2,3
p=7,3 v=-1,2
p=2,4 v=2,-3
p=9,5 v=-3,-3
"""
{{:ok, input}, grid_dims} = if false do
{
KinoAOC.download_puzzle("2024", "14", System.fetch_env!("LB_AOC_SESSION")),
{101, 103}
}
else
{{:ok, example}, {11, 7}}
end
parse_num_pair = fn pair -> pair
|> String.split(",")
|> Enum.map(
fn piece ->
String.replace(piece, ~r/[^\d|^-]/, "") |> String.to_integer()
end)
|> List.to_tuple()
end
parse_robot = fn string ->
parts = String.split(string, "v")
loc = Enum.at(parts, 0) |> parse_num_pair.()
vel = Enum.at(parts, 1) |> parse_num_pair.()
{loc, vel}
end
robots = input |> String.trim() |> String.split("\n")
|> Enum.map(&parse_robot.(&1))
```
```elixir
defmodule Part1 do
def get_final_pos({{xi, yi}, {xv, yv}}, {xsize, ysize}, iter) do
{
rem(rem((xsize + xv) * iter, xsize) + xi, xsize),
rem(rem((ysize + yv) * iter, ysize) + yi, ysize),
}
end
def get_all_final_pos(robots, grid_dims, iter) do
Enum.map(
robots,
fn robot -> get_final_pos(robot, grid_dims, iter) end
)
end
def get_quadrant_counts(finals, mx, my) do
Enum.reduce(
finals, %{}, fn {x, y}, acc ->
cond do
x < mx and y < my -> Map.update(acc, :a, 1, & &1 + 1)
x < mx and y > my -> Map.update(acc, :b, 1, & &1 + 1)
x > mx and y < my -> Map.update(acc, :c, 1, & &1 + 1)
x > mx and y > my -> Map.update(acc, :d, 1, & &1 + 1)
true -> acc
end
end
)
end
end
finals = Part1.get_all_final_pos(robots, grid_dims, 100)
```
```elixir
{xsize, ysize} = grid_dims
{mx, my} = Enum.map(
[xsize, ysize],
& :math.floor(&1 / 2) |> trunc()
)
|> List.to_tuple()
quadrant_counts = Part1.get_quadrant_counts(finals, mx, my)
```
```elixir
result = quadrant_counts |> Map.values() |> Enum.product()
```
## Part 2
```elixir
iters = 0..100
gen_plot = fn iter ->
finals = Part1.get_all_final_pos(robots, grid_dims, iter)
{xs, ys} = Enum.reduce(finals, {[], []}, fn {x, y}, {xs, ys} -> {[x | xs], [y | ys]} end)
VegaLite.new(width: 640, height: 640)
|> VegaLite.data_from_values(x: xs, y: ys)
|> Tucan.scatter("x", "y")
|> Tucan.set_title("#{iter}")
end
Stream.iterate(0, & &1 + 1)
|> Enum.chunk_every(10)
|> Enum.map(
fn some_iters -> some_iters |> Task.async_stream(
fn iter ->
IO.puts("Writing image #{iter}...")
plotfile = gen_plot.(iter) |> Tucan.Export.save!("#{iter}.png")
end
)
|> Task.await_many()
end
)
```
