# Day 19
## Part 1
```elixir
# input = File.read!("19/example.txt") |> String.split("\n")
input = File.read!("19/input.txt") |> String.split("\n")
```
```elixir
defmodule U do
def parse([patterns, "" | designs]) do
{patterns |> String.split(", "), designs |> Enum.filter(fn x -> x != "" end)}
end
end
```
```elixir
{patterns, designs} = U.parse(input)
```
```elixir
patterns = Enum.sort_by(patterns, &String.length/1, :desc)
```
```elixir
defmodule P1 do
def possible?(_, []), do: false
def possible?(design, [p | tail]) do
parts = String.split(design, p, trim: true)
case parts do
[] ->
true
[design] ->
possible?(design, tail)
_ ->
res =
Enum.all?(parts, &possible?(&1, tail))
res || possible?(design, tail)
end
end
end
```
```elixir
Enum.count(designs, fn d ->
res = P1.possible?(d, patterns)
# IO.inspect({d, "=>", res})
res
end)
```
## Part 2
```elixir
defmodule P2 do
def possible(design, patterns) do
{res, _} = possible(design, patterns, %{})
res
end
def possible("", _, memo), do: {1, memo}
def possible(design, patterns, memo) do
case memo[design] do
nil ->
{res, memo} =
Enum.reduce(patterns, {0, memo}, fn p, {acc, memo} ->
case design do
^p <> tail ->
{res, memo} = possible(tail, patterns, memo)
{acc + res, memo}
_ ->
{acc, memo}
end
end)
{res, Map.put(memo, design, res)}
memoized ->
{memoized, memo}
end
end
end
```
```elixir
Enum.reduce(designs, 0, fn d, acc ->
res = P2.possible(d, patterns)
# IO.inspect({d, "=>", res})
acc + res
end)
```
