This commit is contained in:
Shadowfacts 2021-12-12 11:47:16 -05:00
parent 1b1571c323
commit 1bf6e92261
4 changed files with 186 additions and 2 deletions

25
input/day12.txt Normal file
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@ -0,0 +1,25 @@
we-NX
ys-px
ys-we
px-end
yq-NX
px-NX
yq-px
qk-yq
pr-NX
wq-EY
pr-oe
wq-pr
ys-end
start-we
ys-start
oe-DW
EY-oe
end-oe
pr-yq
pr-we
wq-start
oe-NX
yq-EY
ys-wq
ys-pr

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@ -36,7 +36,7 @@ pub fn day11() {
println!("{:?}", grid); println!("{:?}", grid);
for step in 0..100 { for _step in 0..100 {
let (new, flashed) = grid.step(); let (new, flashed) = grid.step();
// println!("after step: {}, new grid: {:?}", step + 1, new); // println!("after step: {}, new grid: {:?}", step + 1, new);
grid = new; grid = new;

158
src/day12.rs Normal file
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@ -0,0 +1,158 @@
use std::collections::{HashMap, HashSet, VecDeque};
use std::fmt::Debug;
use std::fmt::Formatter;
pub fn day12() {
// 10 paths, 36
// let input = r#"
// start-A
// start-b
// A-c
// A-b
// b-d
// A-end
// b-end"#;
// 19 paths, 103
// let input = r#"
// dc-end
// HN-start
// start-kj
// dc-start
// dc-HN
// LN-dc
// HN-end
// kj-sa
// kj-HN
// kj-dc
// "#;
// 226 paths, 3059
// let input = r#"
// fs-end
// he-DX
// fs-he
// start-DX
// pj-DX
// end-zg
// zg-sl
// zg-pj
// pj-he
// RW-he
// fs-DX
// pj-RW
// zg-RW
// start-pj
// he-WI
// zg-he
// pj-fs
// start-RW
// "#;
let input = include_str!("../input/day12.txt");
let graph = parse_graph(&input);
println!("{:?}", graph);
println!("{:?}", count_paths(&graph, false));
println!("{:?}", count_paths(&graph, true));
}
fn parse_graph(input: &'static str) -> Graph {
let mut nodes = HashSet::new();
let mut connections: HashMap<Node, Vec<Node>> = HashMap::new();
for line in input.trim().lines() {
let (a, b) = line.trim().split_once("-").unwrap();
let first: Node = a.into();
let second: Node = b.into();
nodes.insert(first.clone());
nodes.insert(second.clone());
connections
.entry(first.clone())
.or_insert(vec![])
.push(second.clone());
connections.entry(second).or_insert(vec![]).push(first);
}
Graph { nodes, connections }
}
#[derive(PartialEq, Eq, Hash, Clone)]
enum Node {
Start,
End,
Small(&'static str),
Big(&'static str),
}
impl Node {
fn big(&self) -> bool {
match self {
Self::Big(_) => true,
_ => false,
}
}
}
impl Debug for Node {
fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
match self {
Self::Start => write!(f, "start"),
Self::End => write!(f, "end"),
Self::Small(s) | Self::Big(s) => write!(f, "{}", s),
}
}
}
impl From<&'static str> for Node {
fn from(s: &'static str) -> Self {
if s == "start" {
Self::Start
} else if s == "end" {
Self::End
} else if s.chars().all(|c| c.is_uppercase()) {
Self::Big(s)
} else {
Self::Small(s)
}
}
}
#[derive(Debug)]
struct Graph {
nodes: HashSet<Node>,
connections: HashMap<Node, Vec<Node>>,
}
fn count_paths(g: &Graph, allow_visiting_small_twice: bool) -> usize {
let mut queue: VecDeque<(Vec<&Node>, bool)> = VecDeque::new();
queue.push_front((vec![&Node::Start], false));
let mut count = 0;
while let Some((path, mut seen_any_small_twice)) = queue.pop_front() {
let last = path.last().unwrap().clone();
if last == &Node::End {
// println!("{:?}", path);
count += 1;
continue;
}
// current is small and seen current before
if !last.big() && path.iter().rev().skip(1).any(|&n| n == last) {
// if visting small twice is always prohibited (part 1), or we're revisting the start,
// or visiting a _single_ small twice is allowed but we've already done it
if !allow_visiting_small_twice || last == &Node::Start || seen_any_small_twice {
continue;
}
// note that we've now seen a single small cave twice, so any paths descended from this
// one can't do so themselves
seen_any_small_twice = true;
}
for connected in &g.connections[last] {
let mut new_path = path.clone();
new_path.push(connected);
queue.push_back((new_path, seen_any_small_twice));
}
}
count
}

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@ -10,7 +10,8 @@ mod day08;
mod day09; mod day09;
mod day10; mod day10;
mod day11; mod day11;
mod day12;
fn main() { fn main() {
day11::day11(); day12::day12();
} }