ktims/aoc2024
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

day23: add pivot to bron-kerbosch, use more hashsets for speed
Some checks failed
test / AoC 2024 (push) Failing after 4m2s
Details

Browse Source
This commit is contained in:
Keenan Tims 2024-12-23 02:07:22 -08:00
parent 237ca36381
commit 6efb9e0f83
Signed by: ktims
GPG Key ID: 11230674D69038D4
1 changed files with 19 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
src/day23.rs
View File

@ -20,7 +20,7 @@ impl Display for Node {
impl From<[char; 2]> for Node { impl From<[char; 2]> for Node {
fn from(value: [char; 2]) -> Self { fn from(value: [char; 2]) -> Self {
Node(value) Self(value)
} }
} }
@ -33,8 +33,8 @@ impl TryFrom<Vec<char>> for Node {
} }
struct Network { struct Network {
nodes: Vec<Node>, nodes: FxHashSet<Node>,
edges: FxHashMap<Node, Vec<Node>>, edges: FxHashMap<Node, FxHashSet<Node>>,
} }
impl Network { impl Network {
@ -56,6 +56,8 @@ impl Network {
} }
sets sets
} }
// Had to study Wikipedia for this one
// https://en.wikipedia.org/wiki/Bron%E2%80%93Kerbosch_algorithm
fn bron_kerbosch( fn bron_kerbosch(
&self, &self,
r: FxHashSet<Node>, r: FxHashSet<Node>,
@ -65,8 +67,15 @@ impl Network {
let mut results = Vec::new(); let mut results = Vec::new();
if p.is_empty() && x.is_empty() { if p.is_empty() && x.is_empty() {
return vec![r]; return vec![r];
} else if p.is_empty() {
return Vec::new();
} }
let p_iter = p.clone(); // so we can modify p // choose the pivot with the most neighbours, to minimize the size of p_iter
let p_iter = if let Some(pivot) = p.union(&x).max_by(|a, b| self.edges[a].len().cmp(&self.edges[b].len())) {
FxHashSet::from_iter(p.difference(self.edges.get(pivot).unwrap()).copied())
} else {
p.clone()
};
for node in &p_iter { for node in &p_iter {
let mut new_r = r.clone(); let mut new_r = r.clone();
new_r.insert(*node); new_r.insert(*node);
@ -92,7 +101,7 @@ impl Network {
impl From<&str> for Network { impl From<&str> for Network {
fn from(input: &str) -> Self { fn from(input: &str) -> Self {
let mut nodes = Vec::new(); let mut nodes = FxHashSet::default();
let mut edges = FxHashMap::default(); let mut edges = FxHashMap::default();
for line in input.lines() { for line in input.lines() {
let (node1, node2) = line.split_once('-').unwrap(); let (node1, node2) = line.split_once('-').unwrap();
@ -101,13 +110,13 @@ impl From<&str> for Network {
node2.chars().collect_vec().try_into().unwrap(), node2.chars().collect_vec().try_into().unwrap(),
); );
if !nodes.contains(&node1) { if !nodes.contains(&node1) {
nodes.push(node1); nodes.insert(node1);
} }
if !nodes.contains(&node2) { if !nodes.contains(&node2) {
nodes.push(node2); nodes.insert(node2);
} }
edges.entry(node1).or_insert(Vec::new()).push(node2); edges.entry(node1).or_insert(FxHashSet::default()).insert(node2);
edges.entry(node2).or_insert(Vec::new()).push(node1); edges.entry(node2).or_insert(FxHashSet::default()).insert(node1);
} }
Self { nodes, edges } Self { nodes, edges }
} }
@ -120,10 +129,9 @@ fn parse(input: &str) -> Network {
#[aoc(day23, part1)] #[aoc(day23, part1)]
pub fn part1(input: &str) -> i64 { pub fn part1(input: &str) -> i64 {
let network = parse(input); let network = parse(input);
// println!("edges: {:?}", network.edges);
let sets = network.groups_3(); let sets = network.groups_3();
let t_count = sets.iter().filter(|set| set.iter().any(|s| s.0[0] == 't')).count(); let t_count = sets.iter().filter(|set| set.iter().any(|s| s.0[0] == 't')).count();
// println!("groups: {:?}", sets);
t_count as i64 t_count as i64
} }
@ -135,7 +143,6 @@ pub fn part2(input: &str) -> String {
let largest_set = best_sets.iter().max_by(|a, b| a.len().cmp(&b.len())).unwrap(); let largest_set = best_sets.iter().max_by(|a, b| a.len().cmp(&b.len())).unwrap();
let mut largest = largest_set.iter().collect_vec(); let mut largest = largest_set.iter().collect_vec();
largest.sort(); largest.sort();
println!("best: {:?}", largest);
largest.iter().join(",") largest.iter().join(",")
} }