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day14.rs
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day14.rs
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use std::collections::{HashMap, HashSet};
use std::fmt;
use std::str::FromStr;
use crate::parse_lines;
#[derive(Debug, Clone)]
struct Component {
reagent: String,
count: usize,
}
impl Component {
fn new(reagent: String, count: usize) -> Self {
Self { reagent, count }
}
}
#[derive(Clone)]
struct Reaction {
inputs: Vec<Component>,
output: Component,
}
impl fmt::Debug for Reaction {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
for (idx, input) in self.inputs.iter().enumerate() {
if idx < self.inputs.len() - 1 {
write!(f, "{} {}, ", input.count, input.reagent)?;
} else {
write!(f, "{} {} ", input.count, input.reagent)?;
}
}
write!(f, "=> {} {}", self.output.count, self.output.reagent)
}
}
impl Reaction {
fn is_ore_reaction(&self) -> bool {
self.inputs.len() == 1 && self.inputs[0].reagent == "ORE"
}
fn output_count(&self) -> usize {
self.output.count
}
fn output_reagent(&self) -> &str {
&self.output.reagent
}
}
impl FromStr for Reaction {
type Err = String;
fn from_str(input: &str) -> Result<Self, Self::Err> {
let clean = input.trim();
let parts: Vec<_> = clean
.split("=>")
.map(str::trim)
.filter(|p| p.len() > 0)
.collect();
if parts.len() != 2 {
return Err(format!(
"Each reaction should have excatly two parts, {} had {}",
input,
parts.len()
));
}
let inputs = parts[0]
.split(",")
.map(str::trim)
.map(|i| {
let segments: Vec<_> = i.split_whitespace().map(str::trim).collect();
Component::new(
segments[1].to_owned(),
segments[0].parse::<usize>().unwrap(),
)
})
.collect();
let output_segments: Vec<_> = parts[1].split_whitespace().map(str::trim).collect();
if output_segments.len() != 2 {
return Err(format!(
"Each reaction should have an output segment with two parts, {} had {}",
input,
output_segments.len()
));
}
Ok(Self {
inputs,
output: Component::new(
output_segments[1].trim().to_owned(),
output_segments[0].trim().parse::<usize>().unwrap(),
),
})
}
}
struct Reactor {
leftovers: HashMap<String, usize>,
known_reactions: HashMap<String, Reaction>,
ore_used: usize,
}
impl Reactor {
fn new(known_reactions: HashMap<String, Reaction>) -> Self {
Self {
leftovers: HashMap::new(),
known_reactions,
ore_used: 0,
}
}
fn reset(&mut self) {
self.ore_used = 0;
self.leftovers.drain();
}
fn react(&mut self, reaction: Reaction, mut required_output_count: usize) {
// Leftover for this output reagent which we can use
let leftover_for_output = *self.leftovers.get(&reaction.output.reagent).unwrap_or(&0);
if required_output_count <= leftover_for_output {
// Satisfy the whole reaction using leftovers
self.leftovers
.entry(reaction.output.reagent.clone())
.and_modify(|e| *e -= required_output_count)
.or_insert(0);
return;
} else if leftover_for_output > 0 {
// If we have some leftovers, but not enough to fully satisfy the output
// use them before continuing.
self.leftovers
.entry(reaction.output.reagent.clone())
.and_modify(|e| {
*e = 0;
});
required_output_count -= leftover_for_output;
}
let required_reactions =
((required_output_count as f64) / (reaction.output_count() as f64)).ceil() as usize;
if reaction.is_ore_reaction() {
let output_count = required_reactions * reaction.output_count();
let leftover = output_count - required_output_count;
self.leftovers
.entry(reaction.output.reagent.clone())
.and_modify(|e| *e += leftover)
.or_insert(leftover);
self.ore_used += required_reactions * reaction.inputs[0].count;
} else {
for input in reaction.inputs.iter() {
let reaction = self.find_known_reaction(&input.reagent).clone();
self.react(reaction, input.count * required_reactions);
}
let leftover = reaction.output_count() * required_reactions - required_output_count;
self.leftovers
.entry(reaction.output.reagent.clone())
.and_modify(|e| *e += leftover)
.or_insert(leftover);
}
}
fn find_known_reaction(&self, output_reagent: &str) -> &Reaction {
self.known_reactions.get(output_reagent).unwrap()
}
}
pub fn star_one(input: &str) -> usize {
let reactions = parse_lines::<Reaction>(input);
let mut reactor = Reactor::new(
reactions
.map(|r| (r.output_reagent().to_owned(), r))
.collect(),
);
reactor.react(reactor.find_known_reaction("FUEL").clone(), 1);
reactor.ore_used
}
pub fn star_two(input: &str, available_ore: usize) -> usize {
let reactions = parse_lines::<Reaction>(input);
let mut reactor = Reactor::new(
reactions
.into_iter()
.map(|r| (r.output_reagent().to_owned(), r))
.collect(),
);
let mut fuel: f64 = available_ore as f64;
let mut bound = (0.0, available_ore as f64);
let mut ore_use: Vec<(usize, f64)> = vec![];
loop {
reactor.react(
reactor.find_known_reaction("FUEL").clone(),
fuel.floor() as usize,
);
ore_use.push((reactor.ore_used, fuel));
if ore_use
.iter()
.rev()
.nth(2)
.map(|&p| p.1.floor() as usize == fuel.floor() as usize)
.unwrap_or(false)
{
break;
}
if reactor.ore_used > available_ore {
bound = (bound.0, fuel);
fuel = bound.0 + (bound.1 - bound.0) / 2.0;
} else if reactor.ore_used < available_ore {
bound = (fuel, bound.1);
fuel = bound.0 + (bound.1 - bound.0) / 2.0;
}
reactor.reset();
}
let mut last_two: Vec<_> = ore_use.iter().rev().take(2).collect();
last_two.sort_by_key(|v| v.0);
if last_two[0].0 > available_ore {
last_two[1].1.floor() as usize
} else {
last_two[0].1.floor() as usize
}
}
#[cfg(test)]
mod tests {
use super::{star_one, star_two};
const TEST_REACTIONS: &'static [(&'static str, usize, Option<usize>)] = &[
(
"10 ORE => 10 A
1 ORE => 1 B
7 A, 1 B => 1 C
7 A, 1 C => 1 D
7 A, 1 D => 1 E
7 A, 1 E => 1 FUEL",
31,
None,
),
(
"9 ORE => 2 A
8 ORE => 3 B
7 ORE => 5 C
3 A, 4 B => 1 AB
5 B, 7 C => 1 BC
4 C, 1 A => 1 CA
2 AB, 3 BC, 4 CA => 1 FUEL",
165,
None,
),
(
"157 ORE => 5 NZVS
165 ORE => 6 DCFZ
44 XJWVT, 5 KHKGT, 1 QDVJ, 29 NZVS, 9 GPVTF, 48 HKGWZ => 1 FUEL
12 HKGWZ, 1 GPVTF, 8 PSHF => 9 QDVJ
179 ORE => 7 PSHF
177 ORE => 5 HKGWZ
7 DCFZ, 7 PSHF => 2 XJWVT
165 ORE => 2 GPVTF
3 DCFZ, 7 NZVS, 5 HKGWZ, 10 PSHF => 8 KHKGT",
13312,
Some(82892753),
),
(
"
2 VPVL, 7 FWMGM, 2 CXFTF, 11 MNCFX => 1 STKFG
17 NVRVD, 3 JNWZP => 8 VPVL
53 STKFG, 6 MNCFX, 46 VJHF, 81 HVMC, 68 CXFTF, 25 GNMV => 1 FUEL
22 VJHF, 37 MNCFX => 5 FWMGM
139 ORE => 4 NVRVD
144 ORE => 7 JNWZP
5 MNCFX, 7 RFSQX, 2 FWMGM, 2 VPVL, 19 CXFTF => 3 HVMC
5 VJHF, 7 MNCFX, 9 VPVL, 37 CXFTF => 6 GNMV
145 ORE => 6 MNCFX
1 NVRVD => 8 CXFTF
1 VJHF, 6 MNCFX => 4 RFSQX
176 ORE => 6 VJHF
",
180697,
Some(5586022),
),
(
"171 ORE => 8 CNZTR
7 ZLQW, 3 BMBT, 9 XCVML, 26 XMNCP, 1 WPTQ, 2 MZWV, 1 RJRHP => 4 PLWSL
114 ORE => 4 BHXH
14 VRPVC => 6 BMBT
6 BHXH, 18 KTJDG, 12 WPTQ, 7 PLWSL, 31 FHTLT, 37 ZDVW => 1 FUEL
6 WPTQ, 2 BMBT, 8 ZLQW, 18 KTJDG, 1 XMNCP, 6 MZWV, 1 RJRHP => 6 FHTLT
15 XDBXC, 2 LTCX, 1 VRPVC => 6 ZLQW
13 WPTQ, 10 LTCX, 3 RJRHP, 14 XMNCP, 2 MZWV, 1 ZLQW => 1 ZDVW
5 BMBT => 4 WPTQ
189 ORE => 9 KTJDG
1 MZWV, 17 XDBXC, 3 XCVML => 2 XMNCP
12 VRPVC, 27 CNZTR => 2 XDBXC
15 KTJDG, 12 BHXH => 5 XCVML
3 BHXH, 2 VRPVC => 7 MZWV
121 ORE => 7 VRPVC
7 XCVML => 6 RJRHP
5 BHXH, 4 VRPVC => 5 LTCX",
2210736,
Some(460664),
),
];
#[test]
fn test_star_one() {
for &(input, count, _) in TEST_REACTIONS {
let result = star_one(input);
assert_eq!(
result,
count,
"Expected {} to yield output {}. A difference of {}",
input,
count,
(result as isize) - (count as isize),
);
}
}
#[test]
fn test_star_two() {
for &(input, _, fuel) in TEST_REACTIONS {
match fuel {
None => continue,
Some(fuel) => {
let result = star_two(input, 1_000_000_000_000);
assert_eq!(
result,
fuel,
"Expected {} to yield output {}. A difference of {}",
input,
fuel,
(result as isize) - (fuel as isize),
);
}
}
}
}
}