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|
use nom::{
branch::alt,
bytes::complete::tag,
character::complete::{alpha1, line_ending, u32},
combinator::map,
multi::separated_list1,
sequence::tuple,
IResult,
};
use std::{
collections::{BTreeMap, BTreeSet},
fs,
};
fn main() -> Result<(), Box<dyn std::error::Error>> {
let input = fs::read_to_string("inputs/day_16.txt")?;
let nodes = Nodes::parser(&input).unwrap().1;
let mut condensed = nodes.condense();
let mut initial_open_valves = BTreeSet::new();
initial_open_valves.insert(0);
let initial_state = State {
actors: vec![Actor {
position: 0,
time_remaining: 30,
}],
open_valves: initial_open_valves.clone(),
};
dbg!(condensed.find_optimal_pressure_relieved(&initial_state));
let initial_state_with_elephant = State {
actors: vec![
Actor {
position: 0,
time_remaining: 26
};
2
],
open_valves: initial_open_valves,
};
dbg!(condensed.find_optimal_pressure_relieved(&initial_state_with_elephant));
Ok(())
}
#[derive(Debug, Clone)]
struct Nodes {
nodes: BTreeMap<String, Node>,
}
#[derive(Debug, Clone)]
struct Node {
id: String,
flow_rate: u32,
exits: BTreeMap<String, u32>,
}
#[derive(Debug)]
struct CondensedNodes {
nodes: Vec<CondensedNode>,
cache: BTreeMap<State, u32>,
}
#[derive(Debug, Clone)]
struct CondensedNode {
flow_rate: u32,
exits: Vec<u32>,
}
impl Nodes {
fn parser(input: &str) -> IResult<&str, Self> {
map(separated_list1(line_ending, Node::parser), |nodes| Nodes {
nodes: nodes
.into_iter()
.map(|node| (node.id.clone(), node))
.collect(),
})(input)
}
fn condense(&self) -> CondensedNodes {
let node_ids: Vec<String> = self
.nodes
.values()
.filter(|n| n.id == "AA" || n.flow_rate > 0)
.map(|n| n.id.clone())
.collect();
let mut condensed = CondensedNodes {
nodes: self
.nodes
.values()
.filter(|n| n.id == "AA" || n.flow_rate > 0)
.map(|n| CondensedNode {
flow_rate: n.flow_rate,
exits: Vec::new(),
})
.collect(),
cache: BTreeMap::new(),
};
for (id, mut node) in condensed.nodes.iter_mut().enumerate() {
node.exits = node_ids
.iter()
.map(|original_destination_id| {
// +1 because in condensed it includes opening the valve
self.find_shortest_path(&node_ids[id], &original_destination_id) + 1
})
.collect()
}
condensed
}
fn find_shortest_path(&self, from: &str, to: &str) -> u32 {
let mut frontier: BTreeSet<&str> = BTreeSet::new();
let mut explored: BTreeSet<&str> = BTreeSet::new();
let mut distance = 0;
explored.insert(from);
frontier.insert(from);
while !frontier.is_empty() {
let mut next_frontier: BTreeSet<&str> = BTreeSet::new();
distance += 1;
for frontier_point in frontier {
for adjacent_point in self.nodes.get(frontier_point).unwrap().exits.keys() {
if adjacent_point == to {
return distance;
}
if !explored.contains(&adjacent_point.as_ref()) {
explored.insert(adjacent_point);
next_frontier.insert(adjacent_point);
}
}
}
frontier = next_frontier;
}
panic!("Didn't reach end");
}
}
impl Node {
fn parser(input: &str) -> IResult<&str, Self> {
map(
tuple((
tag("Valve "),
alpha1,
tag(" has flow rate="),
u32,
alt((
tag("; tunnels lead to valves "),
tag("; tunnel leads to valve "),
)),
separated_list1(tag(", "), alpha1),
)),
|(_, id, _, flow_rate, _, exits): (_, &str, _, u32, _, Vec<&str>)| Node {
id: id.to_owned(),
flow_rate,
exits: exits
.into_iter()
.map(|destination| (destination.to_owned(), 1))
.collect(),
},
)(input)
}
}
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
struct State {
actors: Vec<Actor>,
open_valves: BTreeSet<usize>,
}
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
struct Actor {
position: usize,
time_remaining: u32,
}
impl State {
fn sort_actors(&mut self) {
self.actors.sort()
}
}
impl CondensedNodes {
fn find_optimal_pressure_relieved(&mut self, state: &State) -> u32 {
let cache_value = self.cache.get(state);
if let Some(cache_value) = cache_value {
return *cache_value;
}
let mut computed_value = 0;
for (actor_i, actor) in state.actors.iter().enumerate() {
let exits_to_investigate: Vec<(usize, u32)> = self.nodes[actor.position]
.exits
.iter()
.enumerate()
.filter(|(destination, distance)| {
!state.open_valves.contains(destination) && **distance <= actor.time_remaining
})
.map(|(destination, distance)| (destination.clone(), distance.clone()))
.collect();
for (destination, distance) in exits_to_investigate {
let mut open_valves = state.open_valves.clone();
open_valves.insert(destination.clone());
let new_actor = Actor {
time_remaining: actor.time_remaining - distance,
position: destination.clone(),
};
let relief_from_this_valve =
self.nodes[destination].flow_rate * new_actor.time_remaining as u32;
let mut actors = state.actors.clone();
actors[actor_i] = new_actor;
let mut state_this_way = State {
actors,
open_valves,
};
state_this_way.sort_actors();
let recursive_relief = self.find_optimal_pressure_relieved(&state_this_way);
let relief = relief_from_this_valve + recursive_relief;
computed_value = computed_value.max(relief);
}
}
self.cache.insert(state.clone(), computed_value);
computed_value
}
}
|
