Added solution for day 8

#!/usr/bin/env python3

# -*- coding: utf-8 -*-

'''

Solution of day 8 of 2023

'''

import time

import argparse as ap

import re

import math

from itertools import cycle

def solve1(file=None, verbose=False, solution=0):

    try:

        expr = re.compile(r"\W+")

        mymap = {}

        with open(file, 'r') as f:

            data = f.read().split('\n\n')

        instructions = data[0]

        nodes = data[1].split('\n')

        for n in nodes[:-1]:

            info = expr.split(n)

            mymap[info[0]] = {"L": info[1], "R": info[2]}

        current = 'AAA'

        instructions = cycle(instructions)

        while current != 'ZZZ':

            solution += 1

            go = next(instructions)

            current = mymap[current][go]

    except FileNotFoundError:

        pass

    return solution

def solve2(file=None, verbose=False, solution=0):

    try:

        expr = re.compile(r"\W+")

        mymap = {}

        starts = []

        end = []

        with open(file, 'r') as f:

            data = f.read().split('\n\n')

        instructions = data[0]

        instructions = cycle(instructions)

        nodes = data[1].split('\n')

        for n in nodes[:-1]:

            info = expr.split(n)

            if info[0][2] == 'A':

                starts.append(info[0])

            mymap[info[0]] = {"L": info[1], "R": info[2]}

        # The trick is actually that all the paths are rather short loops (less

        # than 100k steps) but they should all end on there Z label *at the

        # same time*. The first time this happens is our puzzle answer, and the

        # LCM of all the individual loops.

        # Note that given that there are two examples in this puzzle, this

        # solution will not work on the test set.

        for start in starts:

            for step, go in enumerate(instructions, start=1):

                start = mymap[start][go]

                if start[2] == 'Z':

                    end.append(step)

                    break

        return math.lcm(*end)

    except FileNotFoundError:

        pass

    return solution

def main():

    parser = ap.ArgumentParser()

    parser.add_argument('-i', dest='input', action='store_true')

    parser.add_argument('-v', dest='verbose', action='store_true')

    args = parser.parse_args()

    infile = 'input' if args.input else 'test'

    verbose = args.verbose

    t0 = time.time()

    sol1 = solve1(infile, verbose)

    dt = time.time() - t0

    print(f"Solution 1: {sol1}, Time: {dt}")

    t0 = time.time()

    sol2 = solve2(infile, verbose)

    dt = time.time() - t0

    print(f"Solution 2: {sol2}, Time: {dt}")

    return

if __name__ == "__main__":

    try:

        main()

    except KeyboardInterrupt:

        raise SystemExit("User interruption.")

RL

AAA = (BBB, CCC)

BBB = (DDD, EEE)

CCC = (ZZZ, GGG)

DDD = (DDD, DDD)

EEE = (EEE, EEE)

GGG = (GGG, GGG)

ZZZ = (ZZZ, ZZZ)