Module aoc::y2015::d05

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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?

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