main.py

#

Part 1:

— 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.

import re
#

For example:

def test_part1() -> None:
#

ugknbfddgicrmopn is nice because it has at least three vowels (u...i...o...), a double letter (...dd...), and none of the disallowed substrings.

    assert is_nice("ugknbfddgicrmopn") is True
#

aaa is nice because it has at least three vowels and a double letter, even though the letters used by different rules overlap.

    assert is_nice("aaa") is True
#

jchzalrnumimnmhp is naughty because it has no double letter.

    assert is_nice("jchzalrnumimnmhp") is False
#

haegwjzuvuyypxyu is naughty because it contains the string xy.

    assert is_nice("haegwjzuvuyypxyu") is False
#

dvszwmarrgswjxmb is naughty because it contains only one vowel.

    assert is_nice("dvszwmarrgswjxmb") is False
#

How many strings are nice?


    

  

  

  

    

      

        #
      

      
 Part 1 Solution: 

    

    

      

    

  

  

  

    

      

        #
      

      
Returns the number of times one of the given characters is in the given test
string.


>>> letter_count("aeiou", "abcdde")
2


    

    

      
def letter_count(characters: str, test_string: str) -> int:

    

  

  

  

    

      

        #
      

      
    

    

      
    return sum(test_string.count(char) for char in characters)

    

  

  

  

    

      

        #
      

      
Returns True iff the input string is nice per the problem rules.

    

    

      
def is_nice(test_string: str) -> bool:

    

  

  

  

    

      

        #
      

      
    

    

      
    return all(
        [

    

  

  

  

    

      

        #
      

      
It contains at least three vowels.

    

    

      
            letter_count("aeiou", test_string) >= 3,

    

  

  

  

    

      

        #
      

      
It contains at least one letter that appears twice in a row.

    

    

      
            re.search(r"(\w)\1", test_string) is not None,

    

  

  

  

    

      

        #
      

      
It does not contain the strings ab, cd, pq, or xy.

    

    

      
            not any(bad_str in test_string for bad_str in ["ab", "cd", "pq", "xy"]),
        ]
    )

    

  

  

  

    

      

        #
      

      
Return the number of nice lines in the given multiline string

    

    

      
def part1(input: str) -> int:

    

  

  

  

    

      

        #
      

      
Part 2:


— 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.
    

    • 


    

    

      
    return sum(is_nice(line) for line in input.splitlines())

    

  

  

  

    

      

        #
      

      
    

    

      

    

  

  

  

    

      

        #
      

      
For example:

    

    

      
def test_part2() -> None:

    

  

  

  

    

      

        #
      

      


qjhvhtzxzqqjkmpb is nice because is has a pair that appears twice
(qj) and a letter that repeats with exactly one letter between them
(zxz).



    

    

      
    assert is_nice2("qjhvhtzxzqqjkmpb") is True

    

  

  

  

    

      

        #
      

      


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.



    

    

      
    assert is_nice2("xxyxx") is True

    

  

  

  

    

      

        #
      

      


uurcxstgmygtbstg is naughty because it has a pair (tg) but no repeat
with a single letter between them.



    

    

      
    assert is_nice2("uurcxstgmygtbstg") is False

    

  

  

  

    

      

        #
      

      


ieodomkazucvgmuy is naughty because it has a repeating letter with one
between (odo), but no pair that appears twice.



    

    

      
    assert is_nice2("ieodomkazucvgmuy") is False

    

  

  

  

    

      

        #
      

      
How many strings are nice under these new rules?

    

    

      

    

  

  

  

    

      

        #
      

      
 Part 2 Solution: 

    

    

      

    

  

  

  

    

      

        #
      

      
    

    

      
def is_nice2(test_string: str) -> bool:
    return all(
        [

    

  

  

  

    

      

        #
      

      
It contains a pair of any two letters that appears at least twice
in the string without overlapping

    

    

      
            re.search(r"(\w\w).*\1", test_string) is not None,

    

  

  

  

    

      

        #
      

      
It contains at least one letter which repeats with exactly one
letter between them

    

    

      
            re.search(r"(\w).\1", test_string) is not None,
        ]
    )

    

  

  

  

    

      

        #
      

      
Return the number of nice lines in the given multiline string

    

    

      
def part2(input: str) -> int:

    

  

  

  

    

      

        #
      

      
    

    

      
    return sum(is_nice2(line) for line in input.splitlines())


if __name__ == "__main__":
    puzzle_input = open("input.txt").read()

    

  

  

  

    

      

        #
      

      
Print out part 1 solution

    

    

      
    print("Part 1:", part1(puzzle_input))

    

  

  

  

    

      

        #
      

      
Print out part 2 solution

    

    

      
    print("Part 2:", part2(puzzle_input))