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// This code is slow, about 5 minutes on my laptop
use std::cmp::max;
use std::collections::HashMap;
#[derive(Debug, Clone)]
struct Node {
name: u16,
rate: usize,
neighbors: Vec<u16>
}
#[derive(Debug, Copy, Clone)]
struct MapState {
max_pos: usize,
valves: usize,
pub pos1: usize,
pub pos2: usize
}
#[derive(Debug, Clone)]
struct Map {
index: HashMap<u16, usize>,
state_index: HashMap<u16, usize>,
pressure: Vec<usize>,
nodes: Vec<Node>
}
fn getname(line: &str) -> u16 {
100 * (line.chars().nth(0).unwrap() as u16) +
(line.chars().nth(1).unwrap() as u16)
}
impl Node {
fn from_line(line: &str) -> Node {
let name = getname(&line[6..]);
let j = line.find(';').unwrap();
let rate = line[23..j].parse::<usize>().unwrap();
let mut neighbors = vec![];
let mut i = j+24;
// "tunnels lead to valves" vs "tunnel lead to valve"
// What kind of sadistic animal made these inputs?
if line.chars().nth(i).unwrap() == ' ' { i += 1; }
while i < line.len() {
neighbors.push(getname(&line[i..]));
i += 4;
}
Node { name, rate, neighbors }
}
}
impl MapState {
fn from_usize(i: usize, map: &Map) -> MapState {
let max_pos = map.index.len();
MapState {
max_pos,
valves: i / (max_pos * max_pos),
pos1: i % max_pos,
pos2: (i / max_pos) % max_pos
}
}
fn to_usize(&self) -> usize {
self.max_pos * (self.max_pos * self.valves + self.pos2) + self.pos1
}
fn get_valve(&self, i: usize) -> bool {
self.valves & (1 << i) != 0
}
fn toggle_valve(&mut self, i: usize) {
self.valves ^= 1 << i;
}
}
impl Map {
fn from_stdin() -> Map {
let mut line = String::new();
// Get the nodes
let mut nodes = Vec::<Node>::new();
while std::io::stdin().read_line(&mut line).unwrap() > 0 {
let node = Node::from_line(&line);
if nodes.len() > 0 && node.name == getname("AA") {
nodes.push(nodes[0].clone());
nodes[0] = node;
} else {
nodes.push(node);
}
line.clear();
}
// Compute the node-name-to-index tables
let mut j = 0;
let mut index = HashMap::<u16, usize>::new();
let mut state_index = HashMap::<u16, usize>::new();
let mut pressure = vec![0];
for i in 0..nodes.len() {
index.insert(nodes[i].name, i);
if nodes[i].rate != 0 {
state_index.insert(nodes[i].name, j);
j += 1;
// Pre-compute flow rate for all states with node[i] turned on
for k in 0..pressure.len() {
pressure.push(pressure[k] + nodes[i].rate);
}
}
}
Map { index, state_index, pressure, nodes }
}
fn state_max(&self) -> usize {
self.index.len() * self.index.len() * (1 << self.state_index.len())
}
fn most_pressure(&self, minutes: usize) -> usize {
let n = self.state_max();
let mut t = vec![0 as usize; n];
let mut u = vec![0 as usize; n];
// Setup table for last minute
for s in 0..n {
t[s] = self.pressure[MapState::from_usize(s, self).valves];
u[s] = t[s];
}
// Dynamic programming counting back to 0 minutes
for i in 0..minutes-1 {
// Double buffer technique so we don't have to swap vectors
let (current, next) = if i % 2 == 0 {
(&mut t, &u)
} else {
(&mut u, &t)
};
for s in 0..n {
let mut state = MapState::from_usize(s, self);
let p = self.pressure[state.valves];
let ind1 = self.index[&self.nodes[state.pos1].name];
let ind2 = self.index[&self.nodes[state.pos2].name];
let pos2backup = state.pos2;
let mut k = 0;
// Try turning on valve at pos1
if self.nodes[ind1].rate > 0 {
let si = self.state_index[&self.nodes[ind1].name];
if !state.get_valve(si) {
state.toggle_valve(si);
// Try turning on valve at pos2
if self.nodes[ind2].rate > 0 {
let sj = self.state_index[&self.nodes[ind2].name];
if !state.get_valve(sj) {
state.toggle_valve(sj);
k = max(k, p + next[state.to_usize()]);
state.toggle_valve(sj);
}
}
// Try moving pos2
for w in &self.nodes[ind2].neighbors {
state.pos2 = self.index[w];
k = max(k, p + next[state.to_usize()]);
}
state.pos2 = pos2backup;
state.toggle_valve(si);
}
}
// Try moving pos1
for v in &self.nodes[ind1].neighbors {
state.pos1 = self.index[v];
// Try turning on valve at pos2
if self.nodes[ind2].rate > 0 {
let sj = self.state_index[&self.nodes[ind2].name];
if !state.get_valve(sj) {
state.toggle_valve(sj);
k = max(k, p + next[state.to_usize()]);
state.toggle_valve(sj);
}
}
// Try moving pos2
for w in &self.nodes[ind2].neighbors {
state.pos2 = self.index[w];
k = max(k, p + next[state.to_usize()]);
}
state.pos2 = pos2backup;
}
current[s] = k;
}
}
if 0 == minutes % 2 { t[0] } else { u[0] } // Initial state = 0
}
}
fn main() {
let map = Map::from_stdin();
let result = map.most_pressure(26);
println!("{result}");
}
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