aoc2024day23.py

# === Parsing ===
from collections import defaultdict

edges = defaultdict(set)
with open("input.txt", "r") as f:
    for line in f:
        n1, n2 = line.strip().split("-")
        edges[n1].add(n2)
        edges[n2].add(n1)


# === Part 1 ===
connected = set()
for n1, neighbours in edges.items():
    for n2 in neighbours:
        for n3 in neighbours & edges[n2]:
            connected.add(tuple(sorted((n1, n2, n3))))

count = 0
for group in connected:
    count += any(node.startswith("t") for node in group)

count = sum(any(node.startswith("t") for node in group) for group in connected)

print(count)


# === Part 2 ===
def get_clicks(click, nodes, neighbours):
    # Try to expand the click.
    for idx, node in enumerate(nodes):
        if click <= neighbours[node]:
            yield from get_clicks(click | {node}, nodes[idx:], neighbours)

    yield click


largest_click = max(get_clicks(set(), list(edges.keys()), edges), key=len)
print(",".join(sorted(largest_click)))