advent-of-code/2019/18/src/main.rs
2020-12-01 08:14:33 +01:00

269 lines
8.1 KiB
Rust

use grid::*;
use rayon::prelude::*;
use std::char;
use std::collections::{HashMap, HashSet};
use std::io::{self, BufRead};
use std::ops::Mul;
use std::sync::Mutex;
#[macro_use]
extern crate lazy_static;
#[derive(Hash, PartialEq, Eq, Clone, Debug)]
struct Door(char);
#[derive(Hash, PartialEq, Eq, Clone, Debug)]
struct Key(char);
lazy_static! {
static ref BEST: Mutex<usize> = Mutex::new(999999);
}
fn too_slow(i: usize) -> bool {
let best = BEST.lock().unwrap();
*best < i
}
fn replace(i: usize) {
let mut best = BEST.lock().unwrap();
if i < *best {
println!("Best so far: {}", i);
*best = i;
}
}
fn visit_neighbors(
map: &HashMap<Position2D, char>,
position: Position2D,
steps: usize,
distances: &mut HashMap<Position2D, usize>,
dependencies: &mut HashMap<Key, (HashSet<Key>, HashSet<Door>)>,
door_dependencies: &mut HashMap<Door, HashSet<Door>>,
mut doors: HashSet<Door>,
mut keys: HashSet<Key>,
) {
let c = map.get(&position).unwrap();
if c.is_alphabetic() {
if c.is_lowercase() {
dependencies.insert(Key { 0: *c }, (keys.clone(), doors.clone()));
keys.insert(Key { 0: *c });
}
if c.is_uppercase() {
door_dependencies.insert(Door { 0: *c }, doors.clone());
doors.insert(Door { 0: *c });
}
}
let mut unvisited = Vec::new();
// TODO: fix ownership and make this a single filter().inspect().for_each()
for (_, p) in &position.neighbors() {
match map.get(p) {
Some('#') => (),
_ => {
if distances.get(p).is_none() {
unvisited.push(p.to_owned());
}
}
}
if map.get(p) != Some(&'#') && distances.get(p).is_none() {
unvisited.push(p.to_owned());
}
}
/*
unvisited.into_iter()
.inspect(|p| { distances.insert(p.to_owned(), steps+1);})
.for_each(|p| visit_neighbors(p.to_owned(), steps+1, distances));
*/
for p in &unvisited {
distances.insert(p.to_owned(), steps + 1);
}
for p in &unvisited {
visit_neighbors(
map,
p.to_owned(),
steps + 1,
distances,
dependencies,
door_dependencies,
doors.clone(),
keys.clone(),
);
}
}
fn traverse(
map: &HashMap<Position2D, char>,
start: Position2D,
) -> (
HashMap<Position2D, usize>,
HashMap<Key, (HashSet<Key>, HashSet<Door>)>,
HashMap<Door, HashSet<Door>>,
) {
let mut distances = HashMap::new();
let mut dependencies = HashMap::new();
let mut door_dependencies = HashMap::new();
distances.insert(start, 0usize);
visit_neighbors(
map,
start,
0,
&mut distances,
&mut dependencies,
&mut door_dependencies,
HashSet::new(),
HashSet::new(),
);
(distances, dependencies, door_dependencies)
}
fn find_keys_at_dead_ends(deps: &HashMap<Key, (HashSet<Key>, HashSet<Door>)>) -> HashSet<Key> {
let keydeps: HashSet<_> = deps.iter().flat_map(|(_, (keys, _))| keys).collect();
deps.keys()
.collect::<HashSet<_>>()
.difference(&keydeps)
.into_iter()
.map(|k| k.to_owned().to_owned())
.collect()
}
fn find(map: &HashMap<Position2D, char>, c: char) -> Option<Position2D> {
map.keys().find(|p| map.get(&p) == Some(&c)).copied()
}
fn clear_field(map: &mut HashMap<Position2D, char>, p: &Position2D) {
map.insert(*p, '.');
}
fn remove(map: &mut HashMap<Position2D, char>, k: Key) {
let key_pos = find(map, k.0).unwrap();
clear_field(map, &key_pos);
if let Some(door_pos) = find(map, k.0.to_uppercase().next().unwrap()) {
clear_field(map, &door_pos);
}
}
/*
fn distance_to_door(map: &HashMap<Position2D, char>, k: &Key) -> usize {
let (distances, _, _) = traverse(map, find(map, k.0).unwrap());
let door_pos = find(map, k.0.to_uppercase().next().unwrap());
*door_pos.map(|p| distances.get(&p).unwrap()).unwrap_or(&10)
}
fn distance_to_locked_door(map: &HashMap<Position2D, char>, k: &Key) -> usize {
let (distances, _, doors) = traverse(map, find(map, k.0).unwrap());
*doors
.keys()
.map(|d| find(map, d.0).unwrap())
.map(|p| distances.get(&p).unwrap_or(&9999999999999))
.min()
.unwrap_or(&0)
}
*/
fn next_key(
map: &mut HashMap<Position2D, char>,
pos: &Position2D,
steps: usize,
) -> usize {
if too_slow(steps) {
// println!("Aborting after {} steps", steps);
return 999999;
}
let (distances, dependencies, door_dependencies) = traverse(map, pos.to_owned());
//dbg!(distances.get(&find('c').unwrap()));
if dependencies.len() == 0 {
// println!("End of path after {} steps", steps);
replace(steps);
return steps;
}
let reachable_doors: HashSet<_> = door_dependencies
.iter()
.filter_map(|(door, doors)| if doors.is_empty() { Some(door) } else { None })
.collect();
let mut useful_keys: Vec<_> = dependencies
.iter()
.filter(|(_, (_, d))| d.is_empty())
.filter(|(k, _)| {
reachable_doors.contains(&Door {
0: k.0.to_uppercase().next().unwrap(),
})
})
//.min_by_key(|(k, _)| distances.get(&find(k.0).unwrap()))
//.unwrap()
.map(|(k, _)| {
(
k,
distances
.get(&find(map, k.0).expect("could not find key"))
.expect("No distance to key")
.mul(1),
)
})
.collect();
//.min_by_key(|k| )
let nearest = dependencies.iter()
.filter(|(_, (_, d))| d.is_empty())
.min_by_key(|(k, _)| distances.get(&find(&map, k.0).unwrap()));
let dead_end_keys = find_keys_at_dead_ends(&dependencies);
let mut next: Vec<_> = dead_end_keys
.iter()
.filter(|k| dependencies.get(k).expect("not in deps").1.is_empty())
.map(|k| {
(
k,
distances
.get(&find(map, k.0).expect("could not find key #2"))
.expect("No distance to key #2")
.mul(1),
)
})
//.min_by_key(|k| distances.get(&find(k.0).unwrap()))
//.chain(useful_keys)
.collect();
next.sort_by_key(|(k, n)| *n);//*3 + distance_to_door(map, k));
nearest.map(|(k, _)| next.insert(0, (k, *distances.get(&find(map, k.0).unwrap()).expect("No distance to nearest?"))));
useful_keys.sort_by_key(|(k, n)| *n);
useful_keys.reverse();
useful_keys.pop().map(|k| next.insert(0, k));
//useful_keys.pop().map(|k| next.push(k));
useful_keys.pop().map(|k| next.push(k));
useful_keys.pop().map(|k| next.push(k));
let len = next.len();
next.par_iter()
.take((len.min(4) - 1).max(1))
.map(|(k, _)| {
let mut map2 = map.clone();
let next_pos = find(&map2, k.0).expect("Could not find key #3");
let steps_after_next = steps + distances.get(&next_pos).expect("No distance to key #3");
// collect keys on the way (if any)
for k in &dependencies.get(&k).expect("No dependency found").0 {
remove(&mut map2, k.to_owned());
}
remove(&mut map2, k.to_owned().to_owned());
next_key(&mut map2, &next_pos, steps_after_next)
})
.min()
.unwrap()
}
fn main() {
let map: HashMap<Position2D, char> = io::stdin()
.lock()
.lines()
.enumerate()
.flat_map(move |(y, l)| {
l.unwrap()
.to_owned()
.chars()
.enumerate()
.map(move |(x, c)| ((x, y).into(), c))
.collect::<Vec<_>>()
})
.collect();
let pos = find(&map, '@').unwrap();
//let steps = 0;
//let (_, dependencies, _) = traverse(&map, pos.to_owned());
let p1 = next_key(&mut map.clone(), &pos, 0);
println!("Part 1: {}", p1);
println!("Part 1: {}", BEST.lock().unwrap());
}