Sebastian

It's ramping up. I'm learning new things.

Part 1

with open("input.txt", "r") as f:
    input = f.readlines()

directions = input[0]
input.remove(directions)
input.remove("\n")
nodes = []
for line in input:
    node, edges = line.split(" = (")
    left, right = edges.removesuffix(")\n").split(", ")
    nodes.append(dict(key=node, L=left, R=right))

found = False
key = "AAA"
steps = 0
direction_index = 0
while not found:
    node = next(node for node in nodes if node["key"] == key)
    key = node[directions[direction_index % (len(directions) - 1)]]
    steps += 1
    direction_index += 1
    if key == "ZZZ":
        found = True
print(steps)

Part 2

import math

with open("input.txt", "r") as f:
    input = f.readlines()

directions = input[0]
input.remove(directions)
input.remove("\n")
nodes = []
for line in input:
    node, edges = line.split(" = (")
    left, right = edges.removesuffix(")\n").split(", ")
    nodes.append(dict(key=node, L=left, R=right))

start_nodes = []
for node in nodes:
    if node["key"].endswith("A"):
        start_nodes.append(node)
all_steps = []
for start_node in start_nodes:
    found = False
    steps = 0
    direction_index = 0
    key = start_node["key"]
    while not found:
        node = next(node for node in nodes if node["key"] == key)
        key = node[directions[direction_index % (len(directions) - 1)]]
        steps += 1
        direction_index += 1
        if key.endswith("Z"):
            found = True
    all_steps.append(steps)
print(math.lcm(*all_steps))