## \-\-- 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`{title="John Madden John Madden John Madden"}.
-   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 `236`.

## \-\-- Part Two \-\-- {#part2}

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 `51`.

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

At this point, you should [return to your Advent calendar](/2015) and
try another puzzle.

If you still want to see it, you can [get your puzzle
input](5/input).