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| 1 | +ExUnit.start() |
| 2 | + |
| 3 | +defmodule Lanternfish do |
| 4 | + def load_file() do |
| 5 | + File.read!("../input.txt") |
| 6 | + |> String.split(",", trim: true) |
| 7 | + end |
| 8 | + |
| 9 | + def parse_swarm(input) do |
| 10 | + input |
| 11 | + |> Enum.group_by(& &1) |
| 12 | + |> Enum.map(fn {i, vals} -> {i, Enum.count(vals)} end) |
| 13 | + |> Map.new() |
| 14 | + end |
| 15 | + |
| 16 | + def give_offspring(fish, 0) do |
| 17 | + fish |> Map.delete(9) |
| 18 | + end |
| 19 | + |
| 20 | + def give_offspring(fish, days_remaining) do |
| 21 | + safe_fish = |
| 22 | + fish |
| 23 | + |> Map.put_new(0, 0) |
| 24 | + |> Map.put_new(1, 0) |
| 25 | + |> Map.put_new(2, 0) |
| 26 | + |> Map.put_new(3, 0) |
| 27 | + |> Map.put_new(4, 0) |
| 28 | + |> Map.put_new(5, 0) |
| 29 | + |> Map.put_new(6, 0) |
| 30 | + |> Map.put_new(7, 0) |
| 31 | + |> Map.put_new(8, 0) |
| 32 | + |> Map.put_new(9, 0) |
| 33 | + |
| 34 | + safe_fish |
| 35 | + |> Map.put(7, safe_fish[7] + safe_fish[0]) |
| 36 | + |> Map.put(9, safe_fish[9] + safe_fish[0]) |
| 37 | + |> Enum.map(fn {internal_counter, amount} -> {internal_counter - 1, amount} end) |
| 38 | + |> Map.new() |
| 39 | + |> Map.delete(-1) |
| 40 | + |> Map.delete(9) |
| 41 | + |> give_offspring(days_remaining - 1) |
| 42 | + end |
| 43 | + |
| 44 | + def solve(days) do |
| 45 | + fish = |
| 46 | + load_file() |
| 47 | + |> Enum.map(&Integer.parse/1) |
| 48 | + |> Enum.map(&elem(&1, 0)) |
| 49 | + |> parse_swarm() |
| 50 | + |> give_offspring(days) |
| 51 | + |
| 52 | + Enum.map(fish, fn {_, amount} -> amount end) |
| 53 | + |> Enum.sum() |
| 54 | + end |
| 55 | + |
| 56 | + @spec first() :: Integer |
| 57 | + def first() do |
| 58 | + solve(80) |
| 59 | + end |
| 60 | + |
| 61 | + @spec second() :: Integer |
| 62 | + def second() do |
| 63 | + solve(256) |
| 64 | + end |
| 65 | +end |
| 66 | + |
| 67 | +defmodule LanternfishTest do |
| 68 | + use ExUnit.Case |
| 69 | + |
| 70 | + describe "giveOffsprint/2" do |
| 71 | + test "Initial value" do |
| 72 | + swarm = Lanternfish.parse_swarm([3, 4, 3, 1, 2]) |
| 73 | + assert Lanternfish.give_offspring(swarm, 0) == %{1 => 1, 2 => 1, 3 => 2, 4 => 1} |
| 74 | + end |
| 75 | + |
| 76 | + test "After 1 day" do |
| 77 | + swarm = Lanternfish.parse_swarm([3, 4, 3, 1, 2]) |
| 78 | + |
| 79 | + assert Lanternfish.give_offspring(swarm, 1) == %{ |
| 80 | + 0 => 1, |
| 81 | + 1 => 1, |
| 82 | + 2 => 2, |
| 83 | + 3 => 1, |
| 84 | + 4 => 0, |
| 85 | + 5 => 0, |
| 86 | + 6 => 0, |
| 87 | + 7 => 0, |
| 88 | + 8 => 0 |
| 89 | + } |
| 90 | + end |
| 91 | + |
| 92 | + test "After 2 days" do |
| 93 | + swarm = Lanternfish.parse_swarm([3, 4, 3, 1, 2]) |
| 94 | + |
| 95 | + assert Lanternfish.give_offspring(swarm, 2) == %{ |
| 96 | + 0 => 1, |
| 97 | + 1 => 2, |
| 98 | + 2 => 1, |
| 99 | + 3 => 0, |
| 100 | + 4 => 0, |
| 101 | + 5 => 0, |
| 102 | + 6 => 1, |
| 103 | + 7 => 0, |
| 104 | + 8 => 1 |
| 105 | + } |
| 106 | + end |
| 107 | + end |
| 108 | +end |
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