d16p1

day16/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day16"
+version = "0.1.0"

day16/Cargo.toml

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+[package]
+name = "day16"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day16/input.txt

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+Valve AP has flow rate=0; tunnels lead to valves AA, ON
+Valve QN has flow rate=21; tunnels lead to valves RI, CG
+Valve LK has flow rate=0; tunnels lead to valves XM, AA
+Valve HA has flow rate=0; tunnels lead to valves WH, KF
+Valve DS has flow rate=16; tunnel leads to valve II
+Valve KD has flow rate=0; tunnels lead to valves KG, QB
+Valve JW has flow rate=0; tunnels lead to valves AD, KF
+Valve HU has flow rate=0; tunnels lead to valves UK, CO
+Valve AE has flow rate=10; tunnels lead to valves IR, PT, UV
+Valve XA has flow rate=0; tunnels lead to valves CG, EU
+Valve SE has flow rate=17; tunnels lead to valves YR, AD
+Valve TR has flow rate=0; tunnels lead to valves AL, CS
+Valve BS has flow rate=0; tunnels lead to valves YH, XM
+Valve IJ has flow rate=24; tunnels lead to valves XN, WE
+Valve AA has flow rate=0; tunnels lead to valves LK, AP, IZ, PC, QD
+Valve KG has flow rate=0; tunnels lead to valves KD, CS
+Valve QV has flow rate=0; tunnels lead to valves XM, II
+Valve PC has flow rate=0; tunnels lead to valves AA, YF
+Valve GJ has flow rate=20; tunnel leads to valve RI
+Valve UV has flow rate=0; tunnels lead to valves UK, AE
+Valve IR has flow rate=0; tunnels lead to valves EU, AE
+Valve EU has flow rate=13; tunnels lead to valves IR, DT, XA, ON
+Valve ED has flow rate=0; tunnels lead to valves XN, CO
+Valve DT has flow rate=0; tunnels lead to valves EU, UK
+Valve YE has flow rate=0; tunnels lead to valves XM, WS
+Valve AD has flow rate=0; tunnels lead to valves JW, SE
+Valve WE has flow rate=0; tunnels lead to valves IJ, NA
+Valve UK has flow rate=5; tunnels lead to valves UV, DT, QD, HU
+Valve YR has flow rate=0; tunnels lead to valves OS, SE
+Valve II has flow rate=0; tunnels lead to valves QV, DS
+Valve GT has flow rate=0; tunnels lead to valves CS, MN
+Valve YH has flow rate=0; tunnels lead to valves BS, QB
+Valve BQ has flow rate=0; tunnels lead to valves XM, KF
+Valve OS has flow rate=0; tunnels lead to valves YR, NA
+Valve WH has flow rate=0; tunnels lead to valves QB, HA
+Valve QB has flow rate=4; tunnels lead to valves WH, KD, YH, IZ
+Valve ON has flow rate=0; tunnels lead to valves AP, EU
+Valve IZ has flow rate=0; tunnels lead to valves AA, QB
+Valve MN has flow rate=25; tunnel leads to valve GT
+Valve CG has flow rate=0; tunnels lead to valves XA, QN
+Valve QD has flow rate=0; tunnels lead to valves UK, AA
+Valve AL has flow rate=0; tunnels lead to valves KF, TR
+Valve XN has flow rate=0; tunnels lead to valves ED, IJ
+Valve WS has flow rate=0; tunnels lead to valves YE, CS
+Valve CO has flow rate=18; tunnels lead to valves ED, PT, HU
+Valve PT has flow rate=0; tunnels lead to valves CO, AE
+Valve RI has flow rate=0; tunnels lead to valves QN, GJ
+Valve CS has flow rate=9; tunnels lead to valves YF, GT, WS, TR, KG
+Valve YF has flow rate=0; tunnels lead to valves PC, CS
+Valve NA has flow rate=23; tunnels lead to valves OS, WE
+Valve KF has flow rate=12; tunnels lead to valves HA, AL, JW, BQ
+Valve XM has flow rate=3; tunnels lead to valves LK, QV, YE, BS, BQ

day16/src/main.rs

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+use std::env;
+use std::fs::File;
+use std::io::{BufReader, BufRead};
+use std::collections::{HashMap, HashSet, VecDeque};
+use std::cmp::max;
+use std::str::FromStr;
+
+fn parse_str<T: FromStr>(str: &str) -> Result<(T, usize), <T as FromStr>::Err> {
+    let mut iter = str.chars().peekable();
+    let mut prefix = String::new();
+
+    while let Some(c) = iter.peek()  {
+        if !c.to_string().parse::<T>().is_ok() {
+            break;
+        }
+        prefix.push(iter.next().unwrap());
+    }
+    Ok((prefix.parse::<T>()?, prefix.len()))
+}
+
+#[derive(Debug)]
+struct Valve {
+    rate: u64,
+    links: Vec<(String, u64)>,
+}
+
+fn read_input(fname: &String) -> Result<HashMap<String, Valve>, <u64 as FromStr>::Err> {
+    let file = File::open(fname).expect("cannot open input file");
+    let lines = BufReader::new(file).lines();
+    let mut valves = HashMap::new();
+    for line in lines.flatten() {
+        let name = String::from(&line[6..=7]);
+        let (rate, rate_len) = parse_str::<u64>(&line[23..])?;
+        let links_str = &line[23 + rate_len + 24..];
+        let mut link = String::new();
+        let mut links = Vec::new();
+        let mut iter = links_str.chars();
+        loop {
+            match iter.next() {
+                Some(' ') | Some(',') => continue,
+                None => break,
+                Some(c) => { 
+                    link.push(c);
+                    link.push(iter.next().unwrap());
+                    links.push((link.clone(), 1));
+                    link = String::new();
+                },
+            }
+        }
+        valves.insert(name, Valve { rate, links });
+    }
+    Ok(valves)
+}
+
+fn routes_from(valve: &String, valves: &HashMap<String, Valve>) -> Valve {
+    let mut visited = HashSet::from([valve.clone()]);
+    let mut queue = VecDeque::from([(valve.clone(), 0)]);
+    let mut links = Vec::new();
+    while !queue.is_empty() {
+        let (current_valve, current_cost) = queue.pop_front().unwrap();
+        if current_valve != *valve && valves[&current_valve].rate > 0 {
+            // +1 because it takes 1min to open a valve
+            links.push((current_valve.clone(), current_cost + 1));
+        }
+        for (next_valve, _) in &valves[&current_valve].links {
+            if !visited.contains(next_valve) {
+                queue.push_back((next_valve.clone(), current_cost + 1));
+                visited.insert(next_valve.clone());
+            }
+        }
+    }
+    Valve { rate: valves[valve].rate, links: links }
+}
+
+fn main() {
+    let input_fname = env::args().nth(1).expect("need input file");
+    let valves = read_input(&input_fname).expect("parse error");
+    let mut good_valves = HashMap::new();
+    for (valve_name, valve) in &valves {
+        if valve.rate > 0 || valve_name == "AA" {
+            good_valves.insert(valve_name, routes_from(valve_name, &valves));
+        }
+    }
+
+    let mut max_pressure = 0;
+    let mut queue: VecDeque<(String, u64, u64, HashSet<_>)> = VecDeque::from([(
+        String::from("AA"), 0, 0, HashSet::from([String::from("AA")]))]);
+    while !queue.is_empty() {
+        let (valve, cost, pressure, visited) = queue.pop_front().unwrap();
+        max_pressure = max(max_pressure, pressure);
+        for (hop, hop_cost) in &good_valves[&valve].links {
+            if cost + hop_cost >= 30 || visited.contains(hop) {
+                continue;
+            }
+            let new_cost = cost + hop_cost;
+            let new_pressure = pressure + (30 - new_cost)*valves[hop].rate;
+            let mut new_visited = visited.clone();
+            new_visited.insert(hop.clone());
+            queue.push_back((hop.clone(), new_cost, new_pressure, new_visited));
+        }
+    }
+    println!("Max pressure: {}", max_pressure);
+}

day16/test.txt

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+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