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

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⁂

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

Thanks!

– AlexSchroeder 2016-12-09 11:40 UTC