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use std::collections::HashMap;
use std::io::{self, Read};
use std::str::FromStr;
#[derive(Clone, Copy, PartialOrd, Ord, PartialEq, Eq, Hash)]
struct Chip(u32);
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
struct Bot(u32);
#[derive(Clone, Copy, PartialEq, Eq, Hash)]
struct Output(u32);
#[derive(Clone, Copy, Default)]
struct BotChips(Option<Chip>, Option<Chip>);
impl BotChips {
fn add(&mut self, chip: Chip) {
match (self.0, self.1) {
(None, None) => {
self.0 = Some(chip);
},
(Some(low), None) if low < chip => {
self.1 = Some(chip);
},
(Some(high), None) => {
self.0 = Some(chip);
self.1 = Some(high);
},
_ => panic!("bot has too many chips"),
}
}
fn has_two(&self) -> bool {
self.0.is_some() && self.1.is_some()
}
}
#[derive(Clone, Copy)]
enum Destination {
Bot(Bot),
Output(Output),
}
impl Destination {
fn from_pair(ty: &str, value: u32) -> Result<Self, ()> {
match ty {
"bot" => Ok(Destination::Bot(Bot(value))),
"output" => Ok(Destination::Output(Output(value))),
_ => Err(()),
}
}
}
#[derive(Default)]
struct Instructions {
chips: HashMap<Chip, Bot>,
bots: HashMap<Bot, (Destination, Destination)>,
}
impl FromStr for Instructions {
type Err = ();
fn from_str(s: &str) -> Result<Self, ()> {
let mut instructions = Instructions::default();
for line in s.lines() {
let mut words = line.split(' ');
if words.next() == Some("value") {
let value = words.next().ok_or(())?.parse().map_err(|_| ())?;
let bot = words.nth(3).ok_or(())?.parse().map_err(|_| ())?;
instructions.chips.insert(Chip(value), Bot(bot));
} else {
let bot = words.next().ok_or(())?.parse().map_err(|_| ())?;
let low_type = words.nth(3).ok_or(())?;
let low_value = words.next().ok_or(())?.parse().map_err(|_| ())?;
let high_type = words.nth(3).ok_or(())?;
let high_value = words.next().ok_or(())?.parse().map_err(|_| ())?;
let low = Destination::from_pair(low_type, low_value)?;
let high = Destination::from_pair(high_type, high_value)?;
instructions.bots.insert(Bot(bot), (low, high));
}
}
Ok(instructions)
}
}
#[derive(Default)]
struct State {
outputs: HashMap<Output, Chip>,
bots: HashMap<Bot, BotChips>,
comparisons: HashMap<(Chip, Chip), Bot>,
}
impl State {
fn initialize(&mut self, instructions: &Instructions) {
for (&chip, &bot) in &instructions.chips {
self.bots.entry(bot).or_insert_with(Default::default).add(chip);
}
}
fn step(&mut self, instructions: &Instructions) -> bool {
let active_bots: Vec<Bot> = self.bots.iter()
.filter(|&(_, ref chips)| chips.has_two())
.map(|(&bot, _)| bot)
.collect();
if active_bots.is_empty() {
return false;
}
for bot in active_bots {
let (low, high) = {
let chips = self.bots.get_mut(&bot).unwrap();
(chips.0.take().unwrap(), chips.1.take().unwrap())
};
self.comparisons.insert((low, high), bot);
let &(low_dest, high_dest) = instructions.bots.get(&bot).unwrap();
self.give_to(low_dest, low);
self.give_to(high_dest, high);
}
true
}
fn give_to(&mut self, destination: Destination, chip: Chip) {
match destination {
Destination::Bot(bot) => {
self.bots.entry(bot).or_insert_with(Default::default).add(chip);
},
Destination::Output(output) => {
self.outputs.insert(output, chip);
},
}
}
}
fn solve1(comparison: (Chip, Chip), input: &str) -> Option<Bot> {
let instructions = input.parse().unwrap();
let mut state = State::default();
state.initialize(&instructions);
while state.step(&instructions) { }
state.comparisons.get(&comparison).cloned()
}
fn solve2(input: &str) -> u32 {
let instructions = input.parse().unwrap();
let mut state = State::default();
state.initialize(&instructions);
while state.step(&instructions) { }
state.outputs.get(&Output(0)).unwrap().0
* state.outputs.get(&Output(1)).unwrap().0
* state.outputs.get(&Output(2)).unwrap().0
}
fn main() {
let mut input = String::new();
io::stdin().read_to_string(&mut input).unwrap();
println!("Part 1: {:?}", solve1((Chip(17), Chip(61)), &input));
println!("Part 2: {}", solve2(&input));
}
#[test]
fn part1() {
let input = "
value 5 goes to bot 2
bot 2 gives low to bot 1 and high to bot 0
value 3 goes to bot 1
bot 1 gives low to output 1 and high to bot 0
bot 0 gives low to output 2 and high to output 0
value 2 goes to bot 2
";
assert_eq!(Some(Bot(2)), solve1((Chip(2), Chip(5)), input.trim()));
}
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