advent-of-code/2023/day8.py

import itertools
import math
import sys

lines = sys.stdin.read().splitlines()

sequence = lines[0]
nodes = {
    p[0]: {d: n for d, n in zip("LR", p[1].strip("()").split(", "))}
    for line in lines[2:]
    if (p := line.split(" = "))
}


def path(start: str):
    path = [start]
    it_seq = iter(itertools.cycle(sequence))
    while not path[-1].endswith("Z"):
        path.append(nodes[path[-1]][next(it_seq)])
    return path


# part 1
answer_1 = len(path(next(node for node in nodes if node.endswith("A")))) - 1
print(f"answer 1 is {answer_1}")

# part 2
answer_2 = math.lcm(*(len(path(node)) - 1 for node in nodes if node.endswith("A")))
print(f"answer 2 is {answer_2}")