<!-- livebook:{"persist_outputs":true} -->
# Day 9
```elixir
Mix.install([
{:kino, "~> 0.11.3"}
])
```
## Input
```elixir
example = """
0 3 6 9 12 15
1 3 6 10 15 21
10 13 16 21 30 45
"""
input = Kino.Input.textarea("Input", default: example)
```
## Part 1
```elixir
expected = [18, 28, 68]
```
<!-- livebook:{"output":true} -->
```
[18, 28, 68]
```
```elixir
defmodule Part1 do
def parse(input) do
for history <- String.split(input, "\n", trim: true) do
for n <- String.split(history) do
String.to_integer(n)
end
end
end
def sequence(history, func, acc) do
next =
history
|> Enum.chunk_every(2, 1, :discard)
|> Enum.map(fn [a, b] -> b - a end)
if Enum.all?(next, &(&1 == 0)) do
[func.(history) | acc]
else
sequence(next, func, [func.(history) | acc])
end
end
def run(input) do
for history <- parse(input) do
sequence(history, &List.last/1, [])
|> Enum.reduce(&(&1 + &2))
end
end
end
Part1.run(example) == expected
```
<!-- livebook:{"output":true} -->
```
true
```
```elixir
Kino.Input.read(input)
|> Part1.run()
|> Enum.sum()
|> then(&Kino.Markdown.new("Part 1: #{&1}"))
```
## Part 2
```elixir
expected = [-3, 0, 5]
```
<!-- livebook:{"output":true} -->
```
[-3, 0, 5]
```
```elixir
defmodule Part2 do
def run(input) do
for history <- Part1.parse(input) do
Part1.sequence(history, &List.first/1, [])
|> Enum.reduce(&(&1 - &2))
end
end
end
Part2.run(example) == expected
```
<!-- livebook:{"output":true} -->
```
true
```
```elixir
Kino.Input.read(input)
|> Part2.run()
|> Enum.sum()
|> then(&Kino.Markdown.new("Part 2: #{&1}"))
```
