From 95b654234ff7ccccca7569b374b9b1c6a8ae1144 Mon Sep 17 00:00:00 2001
From: Adrian Groh <adrian.groh@t-online.de>
Date: Mon, 23 Dec 2024 13:15:12 +0100
Subject: [PATCH] Add day23

---
 day23/Cargo.lock  | 63 +++++++++++++++++++++++++++++++++++++++++
 day23/Cargo.toml  |  8 ++++++
 day23/src/main.rs | 71 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 142 insertions(+)
 create mode 100644 day23/Cargo.lock
 create mode 100644 day23/Cargo.toml
 create mode 100644 day23/src/main.rs

diff --git a/day23/Cargo.lock b/day23/Cargo.lock
new file mode 100644
index 0000000..1157acb
--- /dev/null
+++ b/day23/Cargo.lock
@@ -0,0 +1,63 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "day23"
+version = "0.1.0"
+dependencies = [
+ "itertools",
+ "petgraph",
+]
+
+[[package]]
+name = "either"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60b1af1c220855b6ceac025d3f6ecdd2b7c4894bfe9cd9bda4fbb4bc7c0d4cf0"
+
+[[package]]
+name = "equivalent"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5443807d6dff69373d433ab9ef5378ad8df50ca6298caf15de6e52e24aaf54d5"
+
+[[package]]
+name = "fixedbitset"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0ce7134b9999ecaf8bcd65542e436736ef32ddca1b3e06094cb6ec5755203b80"
+
+[[package]]
+name = "hashbrown"
+version = "0.15.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf151400ff0baff5465007dd2f3e717f3fe502074ca563069ce3a6629d07b289"
+
+[[package]]
+name = "indexmap"
+version = "2.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62f822373a4fe84d4bb149bf54e584a7f4abec90e072ed49cda0edea5b95471f"
+dependencies = [
+ "equivalent",
+ "hashbrown",
+]
+
+[[package]]
+name = "itertools"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "413ee7dfc52ee1a4949ceeb7dbc8a33f2d6c088194d9f922fb8318faf1f01186"
+dependencies = [
+ "either",
+]
+
+[[package]]
+name = "petgraph"
+version = "0.6.5"
+source = "git+https://github.com/qoqosz/petgraph?branch=feature%2Fmaximal_cliques#cee17df1398adeae9f4696d3f4caba5662b37d63"
+dependencies = [
+ "fixedbitset",
+ "indexmap",
+]
diff --git a/day23/Cargo.toml b/day23/Cargo.toml
new file mode 100644
index 0000000..eb31ab9
--- /dev/null
+++ b/day23/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "day23"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+itertools = "0.13.0"
+petgraph = { git = "https://github.com/qoqosz/petgraph", branch = "feature/maximal_cliques"}
diff --git a/day23/src/main.rs b/day23/src/main.rs
new file mode 100644
index 0000000..f727481
--- /dev/null
+++ b/day23/src/main.rs
@@ -0,0 +1,71 @@
+use std::collections::{HashMap, HashSet};
+
+use itertools::Itertools;
+use petgraph::algo::maximal_cliques;
+use petgraph::prelude::*;
+
+fn parse(input: &str) -> Vec<(String, String)> {
+    input
+        .lines()
+        .map(|l| l.split_once("-").unwrap())
+        .map(|(a, b)| (a.to_string(), b.to_string()))
+        .collect()
+}
+
+fn build_graph(edges: Vec<(String, String)>) -> UnGraph<String, ()> {
+    let mut graph = UnGraph::new_undirected();
+    let mut node_indices = HashMap::new();
+
+    for (a, b) in edges {
+        let from_index = *node_indices
+            .entry(a.clone())
+            .or_insert_with(|| graph.add_node(a));
+        let to_index = *node_indices
+            .entry(b.clone())
+            .or_insert_with(|| graph.add_node(b));
+        graph.add_edge(from_index, to_index, ());
+    }
+
+    graph
+}
+
+fn part1(graph: &UnGraph<String, ()>) -> usize {
+    let mut cliques3 = HashSet::new();
+    for edge in graph.edge_references() {
+        for &w in graph
+            .neighbors(edge.source())
+            .collect::<HashSet<_>>()
+            .intersection(&graph.neighbors(edge.target()).collect::<HashSet<_>>())
+        {
+            let mut clique3 = [edge.source(), edge.target(), w];
+            clique3.sort_unstable();
+            cliques3.insert(clique3);
+        }
+    }
+    cliques3
+        .iter()
+        .filter(|clique| {
+            clique
+                .iter()
+                .any(|n_idx| graph.node_weight(*n_idx).unwrap().starts_with("t"))
+        })
+        .count()
+}
+
+fn part2(graph: &Graph<String, (), Undirected>) -> String {
+    maximal_cliques(graph)
+        .iter()
+        .max_by_key(|x| x.len())
+        .unwrap()
+        .iter()
+        .map(|n_idx| graph.node_weight(*n_idx).unwrap().to_string())
+        .sorted_unstable()
+        .join(",")
+}
+
+fn main() {
+    let input = parse(include_str!("../input.txt"));
+    let graph = build_graph(input);
+    println!("{}", part1(&graph));
+    println!("{}", part2(&graph));
+}