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hauleth.dev
1<!-- vim:set ft=markdown: -->
2
3<!-- livebook:{"persist_outputs":true} -->
4
5# Day 6
6
7## Section
8
9```elixir
10initial = for i <- 0..8, into: %{}, do: {i, 0}
11
12counts =
13 File.read!("day6.txt")
14 |> String.trim()
15 |> String.split(",")
16 |> Enum.map(&String.to_integer/1)
17 |> Enum.frequencies()
18 |> Map.merge(initial, fn _, a, _ -> a end)
19
20defmodule Day6 do
21 def next(%{0 => next} = population) do
22 1..8
23 |> Map.new(&{&1 - 1, population[&1]})
24 |> Map.merge(%{6 => next, 8 => next}, fn _, v1, v2 -> v1 + v2 end)
25 end
26end
27```
28
29```output
30{:module, Day6, <<70, 79, 82, 49, 0, 0, 7, ...>>, {:next, 1}}
31```
32
33## Task 1
34
35```elixir
361..80
37|> Enum.reduce(counts, fn _, acc -> Day6.next(acc) end)
38|> Map.values()
39|> Enum.sum()
40```
41
42```output
43343441
44```
45
46## Task 2
47
48```elixir
491..256
50|> Enum.reduce(counts, fn _, acc -> Day6.next(acc) end)
51|> Map.values()
52|> Enum.sum()
53```
54
55```output
561569108373832
57```