Day 5 - Advent of Code 2015

Mix.install([:kino, :benchee])

:ok

Links

• Advent of Code (AoC)
• AoC Puzzle Input
• tylerj GitHub

Prompt

--- Day 5: Doesn't He Have Intern-Elves For This? ---

Santa needs help figuring out which strings in his text file are naughty or nice.

A nice string is one with all of the following properties:

• It contains at least three vowels (aeiou only), like aei, xazegov, or aeiouaeiouaeiou.
• It contains at least one letter that appears twice in a row, like xx, abcdde (dd), or aabbccdd (aa, bb, cc, or dd).
• It does not contain the strings ab, cd, pq, or xy, even if they are part of one of the other requirements.

For example:

• ugknbfddgicrmopn is nice because it has at least three vowels (u...i...o...), a double letter (...dd...), and none of the disallowed substrings.
• aaa is nice because it has at least three vowels and a double letter, even though the letters used by different rules overlap.
• jchzalrnumimnmhp is naughty because it has no double letter.
• haegwjzuvuyypxyu is naughty because it contains the string xy.
• dvszwmarrgswjxmb is naughty because it contains only one vowel.

How many strings are nice?

To begin, get your puzzle input.

--- Part Two ---

Realizing the error of his ways, Santa has switched to a better model of determining whether a string is naughty or nice. None of the old rules apply, as they are all clearly ridiculous.

Now, a nice string is one with all of the following properties:

• It contains a pair of any two letters that appears at least twice in the string without overlapping, like xyxy (xy) or aabcdefgaa (aa), but not like aaa (aa, but it overlaps).
• It contains at least one letter which repeats with exactly one letter between them, like xyx, abcdefeghi (efe), or even aaa.

For example:

• qjhvhtzxzqqjkmpb is nice because is has a pair that appears twice (qj) and a letter that repeats with exactly one letter between them (zxz).
• xxyxx is nice because it has a pair that appears twice and a letter that repeats with one between, even though the letters used by each rule overlap.
• uurcxstgmygtbstg is naughty because it has a pair (tg) but no repeat with a single letter between them.
• ieodomkazucvgmuy is naughty because it has a repeating letter with one between (odo), but no pair that appears twice.

How many strings are nice under these new rules?

Although it hasn't changed, you can still get your puzzle input.

Input

input = Kino.Input.textarea("Please paste your input file:")

input = input |> Kino.Input.read()

"zgsnvdmlfuplrubt\nvlhagaovgqjmgvwq\nffumlmqwfcsyqpss\nzztdcqzqddaazdjp\neavfzjajkjesnlsb\nurrvucyrzzzooxhx\nxdwduffwgcptfwad\norbryxwrmvkrsxsr\njzfeybjlgqikjcow\nmayoqiswqqryvqdi\niiyrkoujhgpgkcvx\negcgupjkqwfiwsjl\nzbgtglaqqolttgng\neytquncjituzzhsx\ndtfkgggvqadhqbwb\nzettygjpcoedwyio\nrwgwbwzebsnjmtln\nesbplxhvzzgawctn\nvnvshqgmbotvoine\nwflxwmvbhflkqxvo\ntwdjikcgtpvlctte\nminfkyocskvgubvm\nsfxhhdhaopajbzof\nsofkjdtalvhgwpql\nuqfpeauqzumccnrc\ntdflsbtiiepijanf\ndhfespzrhecigzqb\nxobfthcuuzhvhzpn\nolgjglxaotocvrhw\njhkzpfcskutwlwge\nzurkakkkpchzxjhq\nhekxiofhalvmmkdl\nazvxuwwfmjdpjskj\narsvmfznblsqngvb\nldhkzhejofreaucc\nadrphwlkehqkrdmo\nwmveqrezfkaivvaw\niyphmphgntinfezg\nblomkvgslfnvspem\ncgpaqjvzhbumckwo\nydhqjcuotkeyurpx\nsbtzboxypnmdaefr\nvxrkhvglynljgqrg\nttgrkjjrxnxherxd\nhinyfrjdiwytetkw\nsufltffwqbugmozk\ntohmqlzxxqzinwxr\njbqkhxfokaljgrlg\nfvjeprbxyjemyvuq\ngmlondgqmlselwah\nubpwixgxdloqnvjp\nlxjfhihcsajxtomj\nqouairhvrgpjorgh\nnloszcwcxgullvxb\nmyhsndsttanohnjn\nzjvivcgtjwenyilz\nqaqlyoyouotsmamm\ntadsdceadifqthag\nmafgrbmdhpnlbnks\naohjxahenxaermrq\novvqestjhbuhrwlr\nlnakerdnvequfnqb\nagwpwsgjrtcjjikz\nlhlysrshsmzryzes\nxopwzoaqtlukwwdu\nxsmfrfteyddrqufn\nohnxbykuvvlbbxpf\nbbdlivmchvzfuhoc\nvtacidimfcfyobhf\ntinyzzddgcnmiabd\ntcjzxftqcqrivqhn\nvgnduqyfpokbmzim\nrevkvaxnsxospyow\nydpgwxxoxlywxcgi\nwzuxupbzlpzmikel\nnscghlafavnsycjh\nxorwbquzmgmcapon\nasmtiycegeobfxrn\neqjzvgkxgtlyuxok\nmmjrskloposgjoqu\ngceqosugbkvytfto\nkhivvoxkvhrgwzjl\nqtmejuxbafroifjt\nttmukbmpoagthtfl\nbxqkvuzdbehtduwv\ngvblrpzjylanoggj\ncltewhyjxdbmbtqj\nfbkgedqvomdipklj\nuxvuplhenqawfcjt\nfkdjmayiawdkycva\ngnloqfgbnibzyidh\nkyzorvtopjiyyyqg\ndrckpekhpgrioblt\ntvhrkmbnpmkkrtki\nkhaldwntissbijiz\naoojqakosnaxosom\nxfptccznbgnpfyqw\nmoqdwobwhjxhtrow\nchfwivedutskovri\ngprkyalfnpljcrmi\npwyshpwjndasykst\nxuejivogihttzimd\nbugepxgpgahtsttl\nzufmkmuujavcskpq\nurybkdyvsrosrfro\nisjxqmlxwtqmulbg\npxctldxgqjqhulgz\nhclsekryiwhqqhir\nhbuihpalwuidjpcq\nejyqcxmfczqfhbxa\nxljdvbucuxnnaysv\nirqceqtqwemostbb\nanfziqtpqzqdttnz\ncgfklbljeneeqfub\nzudyqkuqqtdcpmuo\niuvhylvznmhbkbgg\nmpgppmgfdzihulnd\nargwmgcvqqkxkrdi\npdhrfvdldkfihlou\ncbvqnjrvrsnqzfob\nlkvovtsqanohzcmm\nvxoxjdyoylqcnyzt\nkurdpaqiaagiwjle\ngwklwnazaxfkuekn\nrbaamufphjsjhbdl\ntzbrvaqvizhsisbd\npbcqlbfjvlideiub\nhiwoetbfywaeddtx\nfjirczxtuupfywyf\nomeoegeyyospreem\nozbbpupqpsskvrjh\npzvcxkvjdiyeyhxa\nodclumkenabcsfzr\nnpdyqezqdjqaszvm\nyodkwzmrhtexfrqa\nrjcmmggjtactfrxz\nmioxfingsfoimual\naqskaxjjborspfaa\nwientdsttkevjtkf\ntdaswkzckmxnfnct\nvoucjhzvkkhuwoqk\nboaaruhalgaamqmh\niufzxutxymorltvb\npfbyvbayvnrpijpo\nobztirulgyfthgcg\nntrenvhwxypgtjwy\nephlkipjfnjfjrns\npkjhurzbmobhszpx\ngqbnjvienzqfbzvj\nwjelolsrbginwnno\nvotanpqpccxqricj\nbxyuyiglnmbtvehi\nqyophcjfknbcbjrb\nanoqkkbcdropskhj\ntcnyqaczcfffkrtl\nrsvqimuqbuddozrf\nmeppxdrenexxksdt\ntyfhfiynzwadcord\nwayrnykevdmywycf\nmhowloqnppswyzbu\ntserychksuwrgkxz\nxycjvvsuaxsbrqal\nfkrdsgaoqdcqwlpn\nvrabcmlhuktigecp\nxgxtdsvpaymzhurx\nciabcqymnchhsxkc\neqxadalcxzocsgtr\ntsligrgsjtrnzrex\nqeqgmwipbspkbbfq\nvzkzsjujltnqwliw\nldrohvodgbxokjxz\njkoricsxhipcibrq\nqzquxawqmupeujrr\nmizpuwqyzkdbahvk\nsuupfxbtoojqvdca\nywfmuogvicpywpwm\nuevmznxmsxozhobl\nvjbyhsemwfwdxfxk\niyouatgejvecmtin\ntcchwpuouypllcxe\nlgnacnphdiobdsef\nuoxjfzmdrmpojgbf\nlqbxsxbqqhpjhfxj\nknpwpcnnimyjlsyz\nfezotpoicsrshfnh\ndkiwkgpmhudghyhk\nyzptxekgldksridv\npckmzqzyiyzdbcts\noqshafncvftvwvsi\nyynihvdywxupqmbt\niwmbeunfiuhjaaic\npkpkrqjvgocvaxjs\nieqspassuvquvlyz\nxshhahjaxjoqsjtl\nfxrrnaxlqezdcdvd\npksrohfwlaqzpkdd\nravytrdnbxvnnoyy\natkwaifeobgztbgo\ninkcabgfdobyeeom\nywpfwectajohqizp\namcgorhxjcybbisv\nmbbwmnznhafsofvr\nwofcubucymnhuhrv\nmrsamnwvftzqcgta\ntlfyqoxmsiyzyvgv\nydceguvgotylwtea\nbtyvcjqhsygunvle\nusquiquspcdppqeq\nkifnymikhhehgote\nybvkayvtdpgxfpyn\noulxagvbavzmewnx\ntvvpekhnbhjskzpj\nazzxtstaevxurboa\nnfmwtfgrggmqyhdf\nynyzypdmysfwyxgr\niaobtgubrcyqrgmk\nuyxcauvpyzabbzgv\nfbasfnwiguasoedc\nmgmjoalkbvtljilq\nszgkxiqkufdvtksb\nxgfzborpavdmhiuj\nhmuiwnsonvfgcrva\nzolcffdtobfntifb\nmvzgcsortkugvqjr\npbbpgraaldqvzwhs\nzvsxegchksgnhpuv\nkdpdboaxsuxfswhx\njdfggigejfupabth\ntpeddioybqemyvqz\nmxsntwuesonybjby\ntzltdsiojfvocige\nubtdrneozoejiqrv\nfusyucnhncoxqzql\nnlifgomoftdvkpby\npyikzbxoapffbqjw\nhzballplvzcsgjug\nymjyigsfehmdsvgz\nvpqgyxknniunksko\nffkmaqsjxgzclsnq\njcuxthbedplxhslk\nymlevgofmharicfs" <> ...

~c(aeiou)

'aeiou'

Solution

defmodule Day05 do
  defdelegate parse(input), to: __MODULE__.Input

  @vowels ~c(aeiou)

  def part1(input) do
    input
    |> parse()
    |> Enum.count(&nice_part1?/1)
  end

  def part2(input) do
    input
    |> parse()
    |> Enum.count(&nice_part2?/1)
  end

  def nice_part1?(input) do
    has_n_vowels?(input, 3) and
      has_double_letter?(input) and
      no_bad_strings?(input)
  end

  def nice_part2?(input) do
    pair_twice?(input) and sandwich?(input)
  end

  def has_n_vowels?(input, num) do
    Enum.count(input, &(&1 in @vowels)) >= num
  end

  def has_double_letter?([a | [a | _]]), do: true
  def has_double_letter?([_ | tail]), do: has_double_letter?(tail)
  def has_double_letter?([]), do: false

  def no_bad_strings?([?a | [?b | _]]), do: false
  def no_bad_strings?([?c | [?d | _]]), do: false
  def no_bad_strings?([?p | [?q | _]]), do: false
  def no_bad_strings?([?x | [?y | _]]), do: false
  def no_bad_strings?([_ | tail]), do: no_bad_strings?(tail)
  def no_bad_strings?([]), do: true

  def pair_twice?(list, set \\ MapSet.new())

  def pair_twice?([a | [a | [a | _] = tail]], set) do
    if MapSet.member?(set, [a, a]),
      do: true,
      else: pair_twice?(tail, MapSet.put(set, [a, a]))
  end

  def pair_twice?([a | [b | _] = tail], set) do
    if MapSet.member?(set, [a, b]),
      do: true,
      else: pair_twice?(tail, MapSet.put(set, [a, b]))
  end

  def pair_twice?([_ | tail], set), do: pair_twice?(tail, set)
  def pair_twice?([], _), do: false

  def sandwich?([a | [_ | [a | _]]]), do: true
  def sandwich?([_ | tail]), do: sandwich?(tail)
  def sandwich?([]), do: false

  defmodule Input do
    def parse(input) when is_binary(input) do
      input
      |> String.split("\n")
      |> parse()
    end

    def parse(input) when is_list(input) do
      Stream.map(input, &parse_line/1)
    end

    def parse_line(line) do
      String.to_charlist(line)
    end
  end
end

{:module, Day05, <<70, 79, 82, 49, 0, 0, 20, ...>>,
 {:module, Day05.Input, <<70, 79, 82, ...>>, {:parse_line, 1}}}

How many strings are nice?

Your puzzle answer was 238.

Day05.part1(input)

238

How many strings are nice under these new rules?

Your puzzle answer was 69.

Day05.part2(input)

69

Both parts of this puzzle are complete! They provide two gold stars: **

At this point, you should return to your Advent calendar and try another puzzle.

If you still want to see it, you can get your puzzle input.

Tests

ExUnit.start(auto_run: false)

defmodule Day05Test do
  use ExUnit.Case, async: false

  setup_all do
    [
      input: ~w(
        ugknbfddgicrmopn
        aaa
        jchzalrnumimnmhp
        haegwjzuvuyypxyu
        dvszwmarrgswjxmb
      )
    ]
  end

  describe "part1/1" do
    test "returns expected value", %{input: input} do
      assert Day05.nice_part1?('ugknbfddgicrmopn') == true
      assert Day05.nice_part1?('aaa') == true
      assert Day05.nice_part1?('jchzalrnumimnmhp') == false
      assert Day05.nice_part1?('haegwjzuvuyypxyu') == false
      assert Day05.nice_part1?('dvszwmarrgswjxmb') == false

      assert Day05.part1(input) == 2
    end
  end

  describe "part2/1" do
    test "returns expected value" do
      assert Day05.nice_part2?('qjhvhtzxzqqjkmpb') == true
      assert Day05.nice_part2?('xxyxx') == true
      assert Day05.nice_part2?('aaaa') == true
      assert Day05.nice_part2?('aaa') == false
      assert Day05.nice_part2?('uurcxstgmygtbstg') == false
      assert Day05.nice_part2?('ieodomkazucvgmuy') == false
    end
  end
end

ExUnit.run()

..
Finished in 0.00 seconds (0.00s async, 0.00s sync)
2 tests, 0 failures

Randomized with seed 933279

%{excluded: 0, failures: 0, skipped: 0, total: 2}