105 lines
1.8 KiB
Elixir
105 lines
1.8 KiB
Elixir
defmodule Day5 do
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@doc """
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Compares two codepoints for opposite case.
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## Examples
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iex> Day5.react('dabAcCaCBAcCcaDA')
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'dabCBAcaDA'
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"""
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def react(chars) do
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chars
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|> Enum.reduce('', fn
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c, [prev | rest] = s ->
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if oppCase(c, prev) do
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rest
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else
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[c | s]
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end
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c, [] ->
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[c]
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end)
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|> Enum.reverse()
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|> case do
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^chars -> chars
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remaining -> react(remaining)
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end
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end
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@doc """
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Compares two codepoints for opposite case.
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## Examples
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iex> Day5.oppCase(?a, ?A)
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true
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iex> Day5.oppCase(?A, ?a)
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true
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iex> Day5.oppCase(?A, ?A)
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false
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iex> Day5.oppCase(?B, ?A)
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false
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"""
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def oppCase(c1, c2) do
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s1 = <<c1::utf8>>
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s2 = <<c2::utf8>>
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lower1 = String.downcase(s1)
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upper1 = String.upcase(s1)
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lower2 = String.downcase(s2)
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cond do
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lower1 != lower2 -> false
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s1 == lower1 && s1 == s2 -> false
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s1 == upper1 && s1 == s2 -> false
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true -> true
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end
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end
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@doc """
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Compares two codepoints for opposite case.
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## Examples
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iex> Day5.min_length("dabAcCaCBAcCcaDA")
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4
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"""
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def min_length(input) do
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input
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|> String.downcase()
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|> String.to_charlist()
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|> Enum.uniq()
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|> Enum.map(fn c ->
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s = <<c::utf8>>
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str = String.replace(input, s, "")
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str = String.replace(str, String.upcase(s), "")
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input
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|> String.replace(s, "")
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|> String.replace(String.upcase(s), "")
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|> String.to_charlist()
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|> react()
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end)
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|> Enum.min_by(&length/1)
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|> length()
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end
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def parse_input() do
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File.read!("lib/day5/input.txt")
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end
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def part1() do
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parse_input()
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|> String.to_charlist()
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|> react()
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|> length()
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end
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def part2() do
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parse_input()
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|> min_length()
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end
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end |