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use std::collections::{HashMap, HashSet, BinaryHeap};
use std::cmp::Ordering;
use regex::Regex;
use itertools::Itertools;
static DAY: u8 = 16;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", most_pressure(&input, false));
println!("{DAY}b: {}", most_pressure(&input, true));
}
#[derive(PartialEq,Eq)]
struct Valve {
name: String,
flowrate: usize,
tunnels: Vec<String>,
}
impl Valve {
fn new(input: &str) -> Valve {
let re = Regex::new("Valve ([A-Z]+) has flow rate=([0-9]+); tunnels? leads? to valves? ([A-Z, ]+)").unwrap();
let caps = re.captures(input).expect("input should match regex");
let name = String::from(&caps[1]);
let flowrate = caps[2].parse().unwrap();
let tunnels = caps[3].split(", ").map(String::from).collect();
Valve { name, flowrate, tunnels }
}
}
#[derive(Clone, Eq, PartialEq)]
struct State {
cost: usize,
pos: String,
}
/* comparator for priority queue */
impl Ord for State {
fn cmp(&self, other: &Self) -> Ordering {
other.cost.cmp(&self.cost)
}
}
impl PartialOrd for State {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
/* Dijkstra implementation from https://doc.rust-lang.org/std/collections/binary_heap/index.html */
fn dijkstra(map: &HashMap<String,Valve>, from: &str, to: &str) -> usize {
let mut dist = HashMap::new();
let mut heap = BinaryHeap::new();
for pos in map.keys() {
if pos != from {
dist.insert(pos.to_string(), usize::MAX);
}
}
dist.insert(from.to_string(), 0);
heap.push(State { cost: 0, pos: from.to_string() });
while let Some(State { cost, pos }) = heap.pop() {
if pos == to { return cost; }
if cost > dist[&pos] { continue; }
for neigh in &map[&pos].tunnels {
let next = State { cost: cost + 1, pos: neigh.to_string() };
if next.cost < dist[neigh] {
dist.insert(neigh.to_string(), next.cost);
heap.push(next);
}
}
}
panic!("no path found");
}
fn pressure_from(map: &HashMap<&String,&Valve>, distances: &HashMap<(String,String),usize>, from: &str, time: usize, opened: &HashSet<String>) -> usize {
let valves_with_flowrate = map.values()
.filter(|v| v.flowrate > 0)
.map(|v| v.name.clone())
.collect::<Vec<_>>();
let mut max_pressure = 0;
for to in valves_with_flowrate {
if to == from || opened.contains(&to) {
/* no need to travel here if valve already open */
continue;
}
let distance = distances[&(from.to_string(),to.clone())];
if distance >= time {
/* no time left to open another valve at destination */
continue;
}
let new_from = to.clone();
let mut time = time;
time -= 1; // 1 minute to open valve
time -= distance; // time to travel to next valve
let mut opened = opened.clone();
opened.insert(new_from.clone());
let mut pressure = pressure_from(map, distances, &new_from, time, &opened);
pressure += time * map[&new_from].flowrate;
max_pressure = max_pressure.max(pressure);
}
max_pressure
}
fn most_pressure(input: &[String], with_elephant: bool) -> usize {
let map = input.iter()
.map(|x| Valve::new(x))
.map(|x| (x.name.clone(), x))
.collect::<HashMap<String,Valve>>();
let start = "AA";
let mut distances = HashMap::new();
let valves_with_flowrate = map.values()
.filter(|v| v.flowrate > 0)
.collect::<Vec<_>>();
for valve_from in valves_with_flowrate.iter().chain([&map[start]].iter()) {
for valve_to in &valves_with_flowrate {
if valve_from.name == valve_to.name {
continue;
}
let distance = dijkstra(&map, &valve_from.name, &valve_to.name);
distances.insert((valve_from.name.clone(), valve_to.name.clone()), distance);
}
}
let opened = HashSet::new();
let time = match with_elephant {
false => 30,
true => 26,
};
if !with_elephant {
let map = map.iter().collect();
return pressure_from(&map, &distances, start, time, &opened)
}
let mut max_pressure = 0;
for path in valves_with_flowrate.iter().cloned().combinations(valves_with_flowrate.len() / 2) {
let map_you = map.iter()
.filter(|&(_,valve)| path.contains(&valve))
.collect();
let map_elephant = map.iter()
.filter(|&(_,valve)| !path.contains(&valve))
.collect();
let pressure_you = pressure_from(&map_you, &distances, start, time, &opened);
let pressure_elephant = pressure_from(&map_elephant, &distances, start, time, &opened);
max_pressure = max_pressure.max(pressure_you + pressure_elephant);
}
max_pressure
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"Valve AA has flow rate=0; tunnels lead to valves DD, II, BB",
"Valve BB has flow rate=13; tunnels lead to valves CC, AA",
"Valve CC has flow rate=2; tunnels lead to valves DD, BB",
"Valve DD has flow rate=20; tunnels lead to valves CC, AA, EE",
"Valve EE has flow rate=3; tunnels lead to valves FF, DD",
"Valve FF has flow rate=0; tunnels lead to valves EE, GG",
"Valve GG has flow rate=0; tunnels lead to valves FF, HH",
"Valve HH has flow rate=22; tunnel leads to valve GG",
"Valve II has flow rate=0; tunnels lead to valves AA, JJ",
"Valve JJ has flow rate=21; tunnel leads to valve II",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(most_pressure(&input, false), 1651);
assert_eq!(most_pressure(&input, true), 1707);
}
}
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