126 lines
2.6 KiB
Elixir
126 lines
2.6 KiB
Elixir
defmodule Aoc19.Solution.Day04 do
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@name "Day 4: Secure Container"
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@behaviour Solution
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@impl Solution
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def get_name, do: @name
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@impl Solution
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@doc """
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Get the range of numbers from the input.
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## Examples
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iex> Aoc19.Solution.Day04.parse!("1-4")
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1..4
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iex> Aoc19.Solution.Day04.parse!("4-32")
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4..32
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"""
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def parse!(str) do
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[start, stop] =
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str
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|> String.split("-")
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|> Enum.map(&String.to_integer/1)
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start..stop
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end
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@impl Solution
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@doc """
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Solution for the first part of "Day 4: Secure Container".
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"""
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def solve_first_part(range),
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do: range |> Stream.filter(&matches?/1) |> Enum.count()
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@impl Solution
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@doc """
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Solution for the second part of "Day 4: Secure Container".
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"""
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def solve_second_part(range),
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do:
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range
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|> Stream.filter(&matches?/1)
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|> Stream.filter(&larger_groups?/1)
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|> Enum.count()
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@doc """
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Check if password matches all initital criterias.
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## Examples
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iex> Aoc19.Solution.Day04.matches?(8)
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true
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iex> Aoc19.Solution.Day04.matches?(12)
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true
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iex> Aoc19.Solution.Day04.matches?(1123)
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true
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iex> Aoc19.Solution.Day04.matches?(22222)
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true
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iex> Aoc19.Solution.Day04.matches?(122345)
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true
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iex> Aoc19.Solution.Day04.matches?(111123)
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true
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iex> Aoc19.Solution.Day04.matches?(223450)
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false
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iex> Aoc19.Solution.Day04.matches?(123789)
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false
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"""
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def matches?(password) do
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[a, b, c, d, e, f] = number_to_password(password) |> String.codepoints()
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(a == b or b == c or c == d or d == e or e == f) and
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(a <= b and b <= c and c <= d and d <= e and e <= f)
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end
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@doc """
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Check if password digit pairs are not part of a larget group of digits.
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## Examples
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iex> Aoc19.Solution.Day04.larger_groups?(112233)
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true
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iex> Aoc19.Solution.Day04.larger_groups?(123444)
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false
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iex> Aoc19.Solution.Day04.larger_groups?(111122)
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true
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"""
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def larger_groups?(password) do
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washed = Regex.replace(~r/(\d)\1\1+/, number_to_password(password), "")
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case Regex.run(~r/(\d)\1/, washed) do
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nil -> false
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_ -> true
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end
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end
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@doc """
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Takes an integer and turns it to a password by making it a string
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and left pad it with zeros.
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## Examples
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iex> Aoc19.Solution.Day04.number_to_password(8)
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"000008"
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iex> Aoc19.Solution.Day04.number_to_password(123)
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"000123"
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iex> Aoc19.Solution.Day04.number_to_password(123123)
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"123123"
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"""
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def number_to_password(n),
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do: Integer.to_string(n) |> String.pad_leading(6, "0")
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end
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