# Day 11
## Section
```elixir
Mix.install([{:kino, "~> 0.4.1"}])
input = Kino.Input.textarea("Paste your input")
```
```elixir
grid =
Kino.Input.read(input)
|> String.split("\n")
|> Stream.with_index()
|> Stream.flat_map(fn {row, y} ->
row
|> String.split("", trim: true)
|> Stream.map(&Integer.parse/1)
|> Stream.map(fn {n, _} -> n end)
|> Stream.with_index()
|> Stream.map(fn {n, x} -> {{x, y}, {n, false}} end)
end)
|> Enum.into(%{})
```
```elixir
defmodule Day11 do
def step(grid) do
flashed_grid =
grid
|> Enum.map(fn {coords, {n, _}} -> {coords, {n + 1, false}} end)
|> Enum.into(%{})
|> process_flashes
flash_count = Enum.count(flashed_grid, fn {_, {_, flashed}} -> flashed end)
g2 =
Enum.map(flashed_grid, fn
{coords, {_, true}} -> {coords, {0, false}}
{coords, {n, false}} -> {coords, {n, false}}
end)
{flash_count, g2}
end
def process_flashes(grid) do
if about_to_flash?(grid) do
grid
|> Enum.reduce(grid, fn
{{x, y}, {n, false}}, acc when n > 9 ->
acc
|> Map.replace({x, y}, {0, true})
|> update_existing({x - 1, y}, &raise_energy/1)
|> update_existing({x + 1, y}, &raise_energy/1)
|> update_existing({x - 1, y - 1}, &raise_energy/1)
|> update_existing({x + 1, y + 1}, &raise_energy/1)
|> update_existing({x - 1, y + 1}, &raise_energy/1)
|> update_existing({x + 1, y - 1}, &raise_energy/1)
|> update_existing({x, y + 1}, &raise_energy/1)
|> update_existing({x, y - 1}, &raise_energy/1)
_, acc ->
acc
end)
|> process_flashes
else
grid
end
end
defp raise_energy({v, flashed}) do
{v + 1, flashed}
end
defp about_to_flash?(grid) do
Enum.any?(grid, fn
{_, {n, false}} when n > 9 -> true
_ -> false
end)
end
def update_existing(map, key, fun) do
case map do
%{^key => old} -> %{map | key => fun.(old)}
%{} -> map
end
end
end
# %{{0, 0} => 9, {0, 1} => 1, {1, 0} => 1}
# |> Enum.map(fn {coords, n} -> {coords, {n + 1, false}} end)
# |> Enum.into(%{})
# |> Day11.process_flashes()
```
## Part 1
```elixir
Enum.reduce(1..100, {0, grid}, fn _, {flash_count, grid} ->
{new_flashes, updated_grid} = Day11.step(grid)
{flash_count + new_flashes, updated_grid}
end)
```
## Part 2
```elixir
defmodule Part2 do
def find_simul_flash(step, grid) do
{_, updated_grid} = Day11.step(grid)
if Enum.all?(updated_grid, fn {_, {n, _}} -> n === 0 end) do
step + 1
else
find_simul_flash(step + 1, updated_grid)
end
end
end
Part2.find_simul_flash(0, grid)
```
