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# Advent of Code 2023 - Day 09
```elixir
Mix.install([
{:kino, "~> 0.11.0"},
{:kino_aoc, github: "ljgago/kino_aoc"}
])
```
## Input
<!-- livebook:{"attrs":{"assign_to":"puzzle_input","day":"9","session_secret":"AOC_SESSION","year":"2023"},"chunks":null,"kind":"Elixir.KinoAOC.HelperCell","livebook_object":"smart_cell"} -->
```elixir
{:ok, puzzle_input} =
KinoAOC.download_puzzle("2023", "9", System.fetch_env!("LB_AOC_SESSION"))
```
```elixir
history =
puzzle_input
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
String.split(line, " ", trim: true)
|> Enum.map(&String.to_integer(&1))
end)
```
## Part 1
```elixir
extrapolate = fn input, map_fun, reduce_fun ->
Stream.map(input, fn h ->
Stream.unfold(h, fn row ->
next_row =
for i <- 1..(Enum.count(row) - 1) do
Enum.at(row, i) - Enum.at(row, i - 1)
end
unless Enum.all?(row, &(&1 == 0)), do: {map_fun.(row), next_row}
end)
|> Enum.reverse()
|> Enum.reduce(0, reduce_fun)
end)
end
history
|> extrapolate.(&List.last/1, &+/2)
|> Enum.sum()
```
## Part 2
```elixir
history
|> extrapolate.(&List.first/1, &-/2)
|> Enum.sum()
```
[](https://livebook.dev/run?url=https%3A%2F%2Fgithub.com%2Fpehbehbeh%2Fadventofcode%2Fblob%2Fmain%2F2023%2F09.livemd)
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