65 lines
1.5 KiB
Elixir
65 lines
1.5 KiB
Elixir
defmodule Day2 do
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defp read_input do
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Path.expand('input', Path.dirname(__ENV__.file))
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|> File.read!()
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end
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defp parse(input) do
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re = ~r/^(?<min>\d+)-(?<max>\d+) (?<letter>[a-z]): (?<password>[a-z]+)$/
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String.split(input, "\n", trim: true)
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|> Enum.map(fn line ->
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match = Regex.named_captures(re, line)
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%{
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policy: %{
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min: String.to_integer(Map.fetch!(match, "min")),
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max: String.to_integer(Map.fetch!(match, "max")),
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letter: Map.fetch!(match, "letter")
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},
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password: Map.fetch!(match, "password")
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}
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end)
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end
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defp valid_sled?(policy, password) do
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count =
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Enum.reduce(String.codepoints(password), 0, fn char, count ->
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if char == policy.letter do
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count + 1
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else
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count
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end
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end)
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policy.min <= count and count <= policy.max
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end
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defp valid_toboggan?(policy, password) do
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chars = String.codepoints(password)
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l1 = Enum.at(chars, policy.min - 1)
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l2 = Enum.at(chars, policy.max - 1)
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(l1 == policy.letter or l2 == policy.letter) and l1 != l2
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end
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defp xor(a, b) do
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(a or b) and a != b
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end
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def part1 do
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parse(read_input())
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|> Enum.filter(fn %{policy: policy, password: password} -> valid_sled?(policy, password) end)
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|> length()
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end
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def part2 do
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parse(read_input())
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|> Enum.filter(fn %{policy: policy, password: password} ->
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valid_toboggan?(policy, password)
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end)
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|> length()
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end
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end
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Day2.part1() |> IO.inspect()
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Day2.part2() |> IO.inspect()
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