Advent of Code

--- 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?

   Your puzzle answer was 255.

--- 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?

   Your puzzle answer was 55.

   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.

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