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# Day 5
```elixir
Mix.install([
{:kino, "~> 0.8.0"}
])
```
## Puzzle Input
```elixir
input = Kino.Input.textarea("Paste puzzle input")
```
```elixir
defmodule Day5 do
def stack_line?(line), do: String.contains?(line, "[")
defp empty_string?(char), do: char == ""
def line_to_chars(line) do
line
|> String.split("")
|> Enum.reject(&empty_string?/1)
end
def chars_to_chunk(chars) do
chars
|> Enum.chunk_every(4)
end
def join_and_index_chunks(chunks) do
chunks
|> Enum.map(fn chunk -> Enum.join(chunk, "") |> String.trim() end)
|> Enum.with_index(1)
end
# first `.reduce` iteration
def reduce_lines({"", _index}, acc), do: acc
def reduce_lines({value, index}, stacks_map) do
Map.update(stacks_map, index, [value], fn current_value ->
Enum.concat(current_value, [value])
end)
end
def map_instruction([_, move, _, from, _, to]) do
%{
:move => String.to_integer(move),
:from => String.to_integer(from),
:to => String.to_integer(to)
}
end
def apply_instruction_to_stacks(current_instruction, stacks) do
%{from: from, move: move, to: to} = current_instruction
existing = Map.get(stacks, to)
{taken, left_over} =
Map.get(stacks, from)
|> Enum.split(move)
new_to = Enum.concat(Enum.reverse(taken), existing)
%{stacks | from => left_over, to => new_to}
end
def apply_instructions_to_stacks_part_2(current_instruction, stacks) do
%{from: from, move: move, to: to} = current_instruction
existing = Map.get(stacks, to)
{taken, left_over} =
Map.get(stacks, from)
|> Enum.split(move)
new_to = Enum.concat(taken, existing)
%{stacks | from => left_over, to => new_to}
end
end
```
## Part 1
```elixir
[top, bottom] =
Kino.Input.read(input)
|> String.split("\n\n")
stacks =
top
|> String.split("\n")
|> Enum.take_while(&Day5.stack_line?/1)
|> Enum.map(&Day5.line_to_chars/1)
|> Enum.map(&Day5.chars_to_chunk/1)
|> Enum.map(&Day5.join_and_index_chunks/1)
|> Enum.concat()
|> Enum.reduce(%{}, &Day5.reduce_lines/2)
instructions =
bottom
|> String.split("\n")
|> Enum.map(fn instruction -> String.split(instruction, " ") end)
|> Enum.map(&Day5.map_instruction/1)
|> Enum.reduce(stacks, &Day5.apply_instruction_to_stacks/2)
|> Map.values()
|> Enum.map(fn v -> Enum.at(v, 0) end)
|> Enum.map(fn s -> String.replace(s, "[", "") |> String.replace("]", "") end)
|> Enum.join()
```
## Part 2
```elixir
[top, bottom] =
Kino.Input.read(input)
|> String.split("\n\n")
stacks =
top
|> String.split("\n")
|> Enum.take_while(&Day5.stack_line?/1)
|> Enum.map(&Day5.line_to_chars/1)
|> Enum.map(&Day5.chars_to_chunk/1)
|> Enum.map(&Day5.join_and_index_chunks/1)
|> Enum.concat()
|> Enum.reduce(%{}, &Day5.reduce_lines/2)
instructions =
bottom
|> String.split("\n")
|> Enum.map(fn instruction -> String.split(instruction, " ") end)
|> Enum.map(&Day5.map_instruction/1)
|> Enum.reduce(stacks, &Day5.apply_instructions_to_stacks_part_2/2)
|> Map.values()
|> Enum.map(fn v -> Enum.at(v, 0) end)
|> Enum.map(fn s -> String.replace(s, "[", "") |> String.replace("]", "") end)
|> Enum.join()
```
