From 2c2379788d9d2b566a418bd19ca5f10861686ec3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Anders=20Engl=C3=B6f=20Ytterstr=C3=B6m?= <yttan@fastmail.se>
Date: Thu, 2 Jan 2025 22:57:41 +0100
Subject: [PATCH] Solve 2024:23 p1-2 "LAN Party"

Part 1 uses the excellent itertools.combinations().

Part 2 introduces Bron-Kerbosch algorithm to the
util library!
---
 2024-python/aoc.py             | 24 ++++++---------------
 2024-python/output/__init__.py | 11 +++++++++-
 2024-python/output/day_23.py   | 38 ++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 19 deletions(-)
 create mode 100644 2024-python/output/day_23.py

diff --git a/2024-python/aoc.py b/2024-python/aoc.py
index 05e8ceb..11e1df3 100644
--- a/2024-python/aoc.py
+++ b/2024-python/aoc.py
@@ -15,19 +15,12 @@ except ValueError:
     day_no = None
     name = None
 
-print(
-    f"\n\033[95m\033[1mAdvent of Code {year}\033[0m"
-    "\n###################"
-    "\n\n\033[96mby Anders Englöf Ytterström\033[0m"
-)
-
 Path("./input").mkdir(parents=True, exist_ok=True)
 Path("./output").mkdir(parents=True, exist_ok=True)
 
 if day_no and name:
     name = " ".join(name)
     padded_no = day_no.zfill(2)
-    print(f"\n- creating output/day_{padded_no}.py")
     with open("output/day_{}.py".format(padded_no), "w") as s:
         s.write(
             f"""
@@ -75,19 +68,14 @@ if __name__ == "__main__":
 """.strip()
             + "\n"
         )
-    print(
-        f"""
-Done! start coding.
-
-Puzzle link:
-https://adventofcode.com/{year}/day/{day_no}
-
-Puzzle input (copy and paste to input/{day_no.zfill(2)}.txt):
-https://adventofcode.com/{year}/day/{day_no}/input
-    """
-    )
     exit(0)
 
+print(
+    f"\n\033[95m\033[1mAdvent of Code {year}\033[0m"
+    "\n###################"
+    "\n\n\033[96mby Anders Englöf Ytterström\033[0m"
+)
+
 
 stars = 0
 for i in [str(n).zfill(2) for n in range(1, 26)]:
diff --git a/2024-python/output/__init__.py b/2024-python/output/__init__.py
index 22da24f..be90eb8 100644
--- a/2024-python/output/__init__.py
+++ b/2024-python/output/__init__.py
@@ -1,4 +1,3 @@
-import functools
 import re
 
 # Directions/Adjacents for 2D matrices, in the order UP, RIGHT, DOWN, LEFT
@@ -177,3 +176,13 @@ def dijkstras(grid, start, target):
             heapq.heappush(queue, ("stuffs"))
 
     return -1
+
+
+def bk(graph, p, r=set(), x=set()):
+    """Bron-Kerbosch algoritm, no pivot: https://en.wikipedia.org/wiki/Bron%E2%80%93Kerbosch_algorithm"""
+    if not p and not x:
+        yield r
+    while p:
+        v = p.pop()
+        yield from bk(graph, p & set(graph[v]), r | {v}, x & graph[v])
+        x.add(v)
diff --git a/2024-python/output/day_23.py b/2024-python/output/day_23.py
new file mode 100644
index 0000000..536a025
--- /dev/null
+++ b/2024-python/output/day_23.py
@@ -0,0 +1,38 @@
+from collections import defaultdict
+from itertools import combinations
+
+from output import bk
+
+
+def solve(data):
+    graph = defaultdict(set)
+    for line in data.splitlines():
+        a, b = line.strip().split("-")
+        graph[a].add(b)
+        graph[b].add(a)
+    triplets_connected = sum(
+        (
+            a in graph[b]
+            and a in graph[c]
+            and b in graph[a]
+            and b in graph[c]
+            and c in graph[a]
+            and a in graph[b]
+            and any(x.startswith("t") for x in [a, b, c])
+        )
+        for a, b, c in combinations(graph.keys(), r=3)
+    )
+    cliques = bk(graph, set(graph.keys()))
+    max_clique = sorted(cliques, key=lambda i: len(i), reverse=True)[0]
+    lan_password = ",".join(sorted(list(max_clique)))
+    return triplets_connected, lan_password
+
+
+if __name__ == "__main__":
+    with open("./input/23.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)