Advent of Code 2023 - December 8th
Rob van der Leek
Posted on December 8, 2023
In this series, I'll share my progress with the 2023 version of Advent of Code.
Check the first post for a short intro to this series.
You can also follow my progress on GitHub.
December 8th
The puzzle of day 8 was not so hard. I like graph problems, although this was pretty basic.
My pitfall for this puzzle: I have no clue how to find the number that's a common factor for all path lengths. Something similar to Greatest Common Divisor, but what 🤷. In the end a brute force approach worked and doesn't take that long on my M1 laptop.
Solution here, do not click if you want to solve the puzzle first yourself
#!/usr/bin/env python3
import math
with open('input.txt') as infile:
lines = infile.readlines()
directions = [d for d in lines[0].strip()]
graph = {}
for line in lines[2:]:
parts = line.strip().split(' = ')
targets = parts[1][1:-1].split(', ')
graph[parts[0]] = {'L': targets[0], 'R': targets[1]}
dir_idx = 0
steps = 0
nodes = [n for n in graph.keys() if n.endswith('A')]
finished = []
while len([n for n in nodes if not n.endswith('Z')]) > 0:
steps += 1
for idx, n in enumerate(nodes):
if idx in [f[0] for f in finished]:
continue
nodes[idx] = graph[n][directions[dir_idx]]
if nodes[idx].endswith('Z'):
finished.append((idx, steps))
if dir_idx < len(directions) - 1:
dir_idx += 1
else:
dir_idx = 0
for f in finished:
print(f'Finished node {f[0]} in {f[1]} steps')
highest = max([f[1] for f in finished])
total = highest
while True:
all_divisors = True
for f in finished:
if total % f[1] != 0:
all_divisors = False
if all_divisors:
break
else:
total += highest
print(total)
That's it! See you again tomorrow!
Posted on December 8, 2023
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