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hauleth.dev
1# Day 01
2
3```elixir
4Mix.install([:kino_aoc])
5```
6
7## Setup
8
9<!-- livebook:{"attrs":"eyJhc3NpZ25fdG8iOiJwdXp6bGVfaW5wdXQiLCJkYXkiOiIxIiwic2Vzc2lvbl9zZWNyZXQiOiJBRFZFTlRfT0ZfQ09ERV9TRVNTSU9OIiwieWVhciI6IjIwMjUifQ","chunks":null,"kind":"Elixir.KinoAOC.HelperCell","livebook_object":"smart_cell"} -->
10
11```elixir
12{:ok, puzzle_input} =
13 KinoAOC.download_puzzle("2025", "1", System.fetch_env!("LB_ADVENT_OF_CODE_SESSION"))
14```
15
16```elixir
17instructions =
18 puzzle_input
19 |> String.split("\n", trim: true)
20 |> Enum.map(fn <<dir>> <> rest ->
21 num = String.to_integer(rest)
22
23 if dir == ?R do
24 {div(num, 100), rem(num, 100)}
25 else
26 {div(num, 100), -rem(num, 100)}
27 end
28 end)
29```
30
31## Part 1
32
33```elixir
34Enum.reduce(instructions, {50, 0}, fn {_rot, val}, {curr, sum} ->
35 next = Integer.mod(curr + val, 100)
36
37 {next, sum + if(next == 0, do: 1, else: 0)}
38end)
39|> elem(1)
40```
41
42## Part 2
43
44```elixir
45<<0x434C49434B::40>>
46```
47
48```elixir
49Enum.reduce(instructions, {50, 0}, fn {rot, val}, {curr, sum} ->
50 next = curr + val
51
52 pass =
53 cond do
54 curr == 0 and next < 0 -> 0
55 next not in 0..99 -> 1
56 rem(next, 100) == 0 -> 1
57 true -> 0
58 end
59
60 {Integer.mod(next, 100), sum + pass + rot}
61end)
62|> elem(1)
63```
64
65<!-- livebook:{"offset":1234,"stamp":{"token":"XCP.CwH20tHaK8kU6dohgq36CnaY2nnD-3NQc7aO6IAmymU5SEl9dLhm1IihwzVAgdcKHOfAxiDSdAIr5aTfqXWdOCvQRqJrJVUwuKBpAhQvvj9HOgnXBEgEvZz0r_CMSDSOvw","version":2}} -->