Simplify algorithm by unsimplifying graph

2022/Cargo.toml

@@ -10,6 +10,7 @@ ahash = "0.8.2"
 anyhow = "1.0.66"
 clap = { version = "4.0.19", features = ["derive"] }
 itertools = "0.10.5"
+ndarray = "0.15.6"
 nom = "7.1.1"
 strength_reduce = "0.2.4"
 

2022/inputs/16.txt

@@ -0,0 +1,50 @@
+Valve QJ has flow rate=11; tunnels lead to valves HB, GL
+Valve VZ has flow rate=10; tunnel leads to valve NE
+Valve TX has flow rate=19; tunnels lead to valves MG, OQ, HM
+Valve ZI has flow rate=5; tunnels lead to valves BY, ON, RU, LF, JR
+Valve IH has flow rate=0; tunnels lead to valves YB, QS
+Valve QS has flow rate=22; tunnel leads to valve IH
+Valve QB has flow rate=0; tunnels lead to valves QX, ES
+Valve NX has flow rate=0; tunnels lead to valves UH, OP
+Valve PJ has flow rate=0; tunnels lead to valves OC, UH
+Valve OR has flow rate=6; tunnels lead to valves QH, BH, HB, JD
+Valve OC has flow rate=7; tunnels lead to valves IZ, JR, TA, ZH, PJ
+Valve UC has flow rate=0; tunnels lead to valves AA, BY
+Valve QX has flow rate=0; tunnels lead to valves AA, QB
+Valve IZ has flow rate=0; tunnels lead to valves OC, SX
+Valve AG has flow rate=13; tunnels lead to valves NW, GL, SM
+Valve ON has flow rate=0; tunnels lead to valves MO, ZI
+Valve XT has flow rate=18; tunnels lead to valves QZ, PG
+Valve AX has flow rate=0; tunnels lead to valves UH, MO
+Valve JD has flow rate=0; tunnels lead to valves OR, SM
+Valve HM has flow rate=0; tunnels lead to valves TX, QH
+Valve LF has flow rate=0; tunnels lead to valves ZI, UH
+Valve QH has flow rate=0; tunnels lead to valves OR, HM
+Valve RT has flow rate=21; tunnel leads to valve PG
+Valve NE has flow rate=0; tunnels lead to valves VZ, TA
+Valve OQ has flow rate=0; tunnels lead to valves TX, GE
+Valve AA has flow rate=0; tunnels lead to valves QZ, UC, OP, QX, EH
+Valve UH has flow rate=17; tunnels lead to valves PJ, NX, AX, LF
+Valve GE has flow rate=0; tunnels lead to valves YB, OQ
+Valve EH has flow rate=0; tunnels lead to valves AA, MO
+Valve MG has flow rate=0; tunnels lead to valves TX, NW
+Valve YB has flow rate=20; tunnels lead to valves IH, GE, XG
+Valve MO has flow rate=15; tunnels lead to valves EH, ON, AX, ZH, CB
+Valve JR has flow rate=0; tunnels lead to valves ZI, OC
+Valve GL has flow rate=0; tunnels lead to valves AG, QJ
+Valve SM has flow rate=0; tunnels lead to valves JD, AG
+Valve HB has flow rate=0; tunnels lead to valves OR, QJ
+Valve TA has flow rate=0; tunnels lead to valves OC, NE
+Valve PG has flow rate=0; tunnels lead to valves RT, XT
+Valve XG has flow rate=0; tunnels lead to valves CB, YB
+Valve ES has flow rate=9; tunnels lead to valves QB, FL
+Valve BH has flow rate=0; tunnels lead to valves RU, OR
+Valve FL has flow rate=0; tunnels lead to valves SX, ES
+Valve CB has flow rate=0; tunnels lead to valves MO, XG
+Valve QZ has flow rate=0; tunnels lead to valves AA, XT
+Valve BY has flow rate=0; tunnels lead to valves UC, ZI
+Valve ZH has flow rate=0; tunnels lead to valves MO, OC
+Valve OP has flow rate=0; tunnels lead to valves NX, AA
+Valve NW has flow rate=0; tunnels lead to valves MG, AG
+Valve RU has flow rate=0; tunnels lead to valves ZI, BH
+Valve SX has flow rate=16; tunnels lead to valves IZ, FL

2022/src/day16.rs

@@ -1,9 +1,166 @@
+use std::ops::Deref;
+
+use ahash::AHashMap;
 use anyhow::Result;
+use ndarray::Array2;
+use nom::branch::alt;
+use nom::bytes::complete::tag;
+use nom::character::complete::alpha1;
+use nom::character::complete::newline;
+use nom::combinator::into;
+use nom::multi::many1;
+use nom::multi::separated_list1;
+use nom::sequence::preceded;
+use nom::sequence::terminated;
+use nom::sequence::tuple;
+use nom::IResult;
 
-pub fn part1(_input: &[u8]) -> Result<String> {
-    anyhow::bail!("not implemented")
+use crate::common::parse_input;
+
+type ParsedValve<'a> = (&'a [u8], u16, Vec<&'a [u8]>);
+
+type ParsedNetwork<'a> = Vec<ParsedValve<'a>>;
+
+#[derive(Debug)]
+struct SimpleNetwork {
+    valves: Vec<SimpleValve>,
+    start: usize,
+    useful: usize,
 }
 
-pub fn part2(_input: &[u8]) -> Result<String> {
-    anyhow::bail!("not implemented")
+impl Deref for SimpleNetwork {
+    type Target = [SimpleValve];
+
+    fn deref(&self) -> &Self::Target {
+        &self.valves
+    }
+}
+
+#[derive(Debug)]
+struct SimpleValve {
+    connected: Vec<usize>,
+    flow: u16,
+}
+
+impl From<ParsedNetwork<'_>> for SimpleNetwork {
+    fn from(mut parsed: ParsedNetwork) -> Self {
+        // Make sure the positive numbers are in the front
+        parsed.sort_by(|a, b| b.1.cmp(&a.1));
+
+        let mapping: AHashMap<_, _> = parsed
+            .iter()
+            .enumerate()
+            .map(|(index, (name, _, _))| (*name, index))
+            .collect();
+
+        let useful = parsed.iter().filter(|(_, flow, _)| *flow > 0).count();
+
+        Self {
+            valves: parsed
+                .into_iter()
+                .map(|(_, flow, connected)| {
+                    let connected = connected.into_iter().map(|name| mapping[&name]).collect();
+
+                    SimpleValve { flow, connected }
+                })
+                .collect(),
+            start: mapping[&b"AA"[..]],
+            useful,
+        }
+    }
+}
+
+fn parse_network(input: &[u8]) -> IResult<&[u8], ParsedNetwork> {
+    let parse_network = terminated(
+        tuple((
+            // Parse the name of the valve
+            preceded(tag("Valve "), alpha1),
+            // Parse the flow of the valve
+            preceded(tag(" has flow rate="), nom::character::complete::u16),
+            // Parse the connections
+            preceded(
+                // Did you really have to distinguish plural
+                alt((
+                    tag("; tunnels lead to valves "),
+                    tag("; tunnel leads to valve "),
+                )),
+                separated_list1(tag(", "), alpha1),
+            ),
+        )),
+        newline,
+    );
+
+    many1(parse_network)(input)
+}
+
+pub fn part1(input: &[u8]) -> Result<String> {
+    let network: SimpleNetwork = parse_input(input, into(parse_network))?;
+
+    let (valves_available, dp) = run_optimization(&network, 30);
+
+    Ok(dp[(network.start, valves_available)].to_string())
+}
+
+fn run_optimization(network: &SimpleNetwork, time: usize) -> (usize, Array2<u16>) {
+    let valves_available = (1 << network.useful) - 1;
+    let mut cur = Array2::zeros((network.len(), valves_available + 1));
+    let mut prev = cur.clone();
+
+    for time_remaining in 1..time {
+        for pos in 0..network.len() {
+            let bit = 1 << pos;
+            for open_valves in 0..=valves_available {
+                let optimal = if (bit & open_valves) != 0 && time_remaining > 2 {
+                    prev[(pos, open_valves - bit)] + time_remaining as u16 * network[pos].flow
+                } else {
+                    0
+                };
+
+                cur[(pos, open_valves)] = network[pos]
+                    .connected
+                    .iter()
+                    .map(|&other| prev[(other, open_valves)])
+                    .fold(optimal, Ord::max);
+            }
+        }
+
+        std::mem::swap(&mut prev, &mut cur);
+    }
+    (valves_available, prev)
+}
+
+pub fn part2(input: &[u8]) -> Result<String> {
+    let network: SimpleNetwork = parse_input(input, into(parse_network))?;
+
+    let (valves_available, dp) = run_optimization(&network, 26);
+
+    // Find the minimum of all combinations of your work/elephant's work
+    let best = (0..=valves_available)
+        .map(|my_valves| {
+            let elephant_valves = valves_available - my_valves;
+
+            dp[(network.start, my_valves)] + dp[(network.start, elephant_valves)]
+        })
+        .max()
+        .unwrap_or(0);
+
+    // Guesses: 1802 (too low)
+    Ok(best.to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const SAMPLE: &[u8] = include_bytes!("samples/16.txt");
+
+    #[test]
+    fn sample_part1() {
+        assert_eq!(part1(SAMPLE).unwrap(), "1651");
+    }
+
+    #[test]
+    fn sample_part2() {
+        assert_eq!(part2(SAMPLE).unwrap(), "1707");
+    }
 }

2022/src/samples/16.txt

@@ -0,0 +1,10 @@
+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