2016-12-09 Advent of Code in Python

It was pretty easy to slide back into Python. I used Python 3 because I hear that’s what one ought to use. I really like the Python documentation. A very good read. You can tell because I prefer reading the documentation to searching for examples on StackExchange. Well done!

So, Advent of Code, day 7, part 1: Count how many strings comply with the following specification:

Advent of Code

1. Each string consists of some letters, with one or more sections in square brackets, e.g. `alex[berta]otto`.

2. The string must have a four character palindrome consisting of two different letters *outside* square brackets, e.g. `otto` in the example above.

3. No such string may be found withing square brackets.

4. There may be multiple sets of square brackets within the string.import sys import redef has_palindrome(word): m = re.search(r"([a-z])([a-z])\2\1", word) # aaaa is not a valid palindrome if (m and m.group(1) != m.group(2)): return 1def check_line(line): inside = 0 outside = 0 parts = re.findall('([a-z]+)(?:[([a-z]+)])?', line) for part in parts: if (has_palindrome(part[0])): outside += 1 if (has_palindrome(part[1])): inside += 1 return inside == 0 and outside > 0def check_input(): sum = 0 for line in sys.stdin: if check_line(line): sum += 1 return sumif **name** == '**main**': print (str(check_input()))

Part 2: Count how many strings comply with the following specification:

1. Each string consists of some letters, with one or more sections in square brackets, e.g. `ala[lala]otto`.

2. The string must have a three character palindrome consisting of two different letters *outside* square brackets, e.g. `ala`, and a matching inverted three character palindrome *inside* any of the square brackets, e.g. `lal` in the example above.

3. There may be multiple sets of square brackets within the string.

This was surprisingly more difficult!

import sys
import re

def check_line(line):
    inside = []
    outside = []
    for part in re.findall('([a-z]+)(?:\[([a-z]+)\])?', line):
        outside.append(part[0])
        if part[1]:
            inside.append(part[1])
    for word in outside:
        for i in range(len(word) - 2):
            if word[i] == word[i+2] and word[i] != word[i+1]:
                for other in inside:
                    if re.search(word[i+1] + word[i] + word[i+1], other):
                        return 1

def check_input():
    sum = 0
    for line in sys.stdin:
        if check_line(line):
            sum += 1
    return sum

if __name__ == '__main__':
    print (str(check_input()))

Call using `python part1.py < data` and `python part2.py < data`.

I also wondered about an integrated Python debugger for Emacs. Sadly, I used print statements all over the place as I was searching for bugs.

​#Python ​#Advent of Code ​#Programming

Comments

(Please contact me if you want to remove your comment.)

⁂

You can use the fileinput module for reading the data: https://docs.python.org/2/library/fileinput.html

https://docs.python.org/2/library/fileinput.html

Instead of for i in range(len(word) - 2): you can do something like for a, b, c in zip(word, word[1:], word[2:]):

Instead of re.search you can simply use the “in” operator.

– Radomir Dopieralski 2016-12-09 08:23 UTC

Radomir Dopieralski

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Thanks!

– AlexSchroeder 2016-12-09 11:40 UTC