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day20.rs
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day20.rs
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use crate::data::load;
use crate::math_utils;
use std::collections::{HashMap, HashSet, VecDeque};
use thiserror::Error;
#[derive(Error, Debug, PartialEq, Eq)]
pub enum PuzzleErr {
#[error("Input parsing error")]
ParseInputError,
#[error("Runtime error")]
RuntimeError,
#[error("An expectation required for Part 2 was violated")]
Part2ExpectationViolated,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum Pulse {
High,
Low,
}
#[derive(Debug, Clone)]
struct PulseMsg {
from: String,
to: String,
pulse: Pulse,
}
trait Receiver {
fn receive(&mut self, in_pulse: &PulseMsg) -> Option<VecDeque<PulseMsg>>;
}
#[derive(Debug, Clone)]
struct Broadcast {
name: String,
receivers: Vec<String>,
}
fn _parse_after_arrow(line: &str) -> Vec<String> {
line.trim()
.split("->")
.nth(1)
.unwrap()
.trim()
.split(", ")
.map(|s| s.to_string())
.collect::<Vec<_>>()
}
impl Broadcast {
fn new(receivers: &[String]) -> Self {
Broadcast {
name: "broadcaster".to_string(),
receivers: receivers.to_owned(),
}
}
fn from(line: &str) -> Self {
let receivers = _parse_after_arrow(line);
Self::new(&receivers)
}
}
impl Receiver for Broadcast {
fn receive(&mut self, in_pulse: &PulseMsg) -> Option<VecDeque<PulseMsg>> {
Option::Some(
self.receivers
.iter()
.map(|r| PulseMsg {
from: self.name.clone(),
to: r.clone(),
pulse: in_pulse.pulse,
})
.collect::<VecDeque<_>>(),
)
}
}
#[derive(Debug, Clone)]
struct Conjunction {
name: String,
memory: HashMap<String, Pulse>,
receivers: Vec<String>,
}
impl Conjunction {
fn new(name: &str, receivers: &[String]) -> Self {
Self {
name: name.to_string(),
memory: HashMap::new(),
receivers: receivers.to_owned(),
}
}
fn from(line: &str) -> Self {
let name = line.split("->").nth(0).unwrap().replace('&', "");
let receivers = _parse_after_arrow(line);
Self::new(name.trim(), &receivers)
}
fn add_input(&mut self, new_input: &str) {
self.memory.insert(new_input.to_string(), Pulse::Low);
}
fn add_inputs(&mut self, new_inputs: &HashSet<&str>) {
new_inputs.iter().for_each(|i| self.add_input(i))
}
}
impl Receiver for Conjunction {
fn receive(&mut self, in_pulse: &PulseMsg) -> Option<VecDeque<PulseMsg>> {
self.memory.insert(in_pulse.from.clone(), in_pulse.pulse);
let out_pulse = match self.memory.values().all(|p| p == &Pulse::High) {
true => Pulse::Low,
false => Pulse::High,
};
Option::Some(
self.receivers
.iter()
.map(|r| PulseMsg {
from: self.name.clone(),
to: r.clone(),
pulse: out_pulse,
})
.collect::<VecDeque<_>>(),
)
}
}
#[derive(Debug, Clone)]
struct FlipFlop {
name: String,
state: bool, // true = "on", false = "off"
receivers: Vec<String>,
}
impl FlipFlop {
fn new(name: &str, receivers: &[String]) -> Self {
Self {
name: name.to_string(),
state: false,
receivers: receivers.to_owned(),
}
}
fn from(line: &str) -> Self {
let name = line.split("->").nth(0).unwrap().replace('%', "");
let receivers = _parse_after_arrow(line);
Self::new(name.trim(), &receivers)
}
}
impl Receiver for FlipFlop {
fn receive(&mut self, in_pulse: &PulseMsg) -> Option<VecDeque<PulseMsg>> {
log::trace!(
"FlipFlip {} received {:?} pulse.",
self.name,
in_pulse.pulse
);
if in_pulse.pulse == Pulse::High {
return None;
}
let out_pulse = match self.state {
false => Pulse::High,
true => Pulse::Low,
};
self.state = !self.state;
Option::Some(
self.receivers
.iter()
.map(|r| PulseMsg {
from: self.name.clone(),
to: r.clone(),
pulse: out_pulse,
})
.collect::<VecDeque<_>>(),
)
}
}
#[derive(Debug, Clone)]
struct Output {
name: String,
}
impl Output {
fn new() -> Self {
Self {
name: "output".to_string(),
}
}
}
impl Receiver for Output {
fn receive(&mut self, _: &PulseMsg) -> Option<VecDeque<PulseMsg>> {
Option::None
}
}
#[derive(Debug, Clone)]
enum Module {
B(Broadcast),
C(Conjunction),
F(FlipFlop),
O(Output),
}
fn _parse_input_line(line: &str) -> Result<Module, PuzzleErr> {
if line.starts_with("broadcaster") {
Ok(Module::B(Broadcast::from(line)))
} else if line.starts_with('%') {
Ok(Module::F(FlipFlop::from(line)))
} else if line.starts_with('&') {
Ok(Module::C(Conjunction::from(line)))
} else {
Err(PuzzleErr::ParseInputError)
}
}
fn parse_input(input: &str) -> Result<HashMap<String, Module>, PuzzleErr> {
// Parse the individual modules defined on each line.
let mut modules = input
.trim()
.lines()
.map(_parse_input_line)
.collect::<Result<Vec<_>, PuzzleErr>>()?;
// Manually add the `Output` module.
modules.push(Module::O(Output::new()));
// Convert the vector into a dictionary.
let mut mapping = modules
.into_iter()
.map(|m| {
let x: (String, Module) = match m {
Module::B(ref a) => (a.name.clone(), m),
Module::C(ref a) => (a.name.clone(), m),
Module::F(ref a) => (a.name.clone(), m),
Module::O(ref a) => (a.name.clone(), m),
};
x
})
.collect::<HashMap<String, Module>>();
// Get inputs for Conjugation modules.
let mut receiver_connections = HashMap::<String, HashSet<&str>>::new();
let duplicate_mapping = mapping.clone();
for (name, module) in duplicate_mapping.iter() {
let recievers = match module {
Module::B(b) => b.receivers.clone(),
Module::F(f) => f.receivers.clone(),
Module::C(c) => c.receivers.clone(),
_ => Vec::new(),
};
recievers.iter().for_each(|r| {
receiver_connections
.entry(r.to_string())
.and_modify(|s| {
s.insert(name.as_str());
})
.or_insert(HashSet::from_iter([name.as_str()]));
});
}
for (receiver, input_mods) in receiver_connections.iter() {
if let Some(Module::C(c)) = mapping.get_mut(receiver) {
c.add_inputs(input_mods)
}
}
Ok(mapping)
}
struct PulseCounter {
low: u32,
high: u32,
}
impl PulseCounter {
fn new() -> Self {
Self { low: 0, high: 0 }
}
fn track(&mut self, pulse_msg: &PulseMsg) {
match pulse_msg.pulse {
Pulse::Low => self.low += 1,
Pulse::High => self.high += 1,
}
}
}
pub fn puzzle_1(input: &str, n_button_presses: u32) -> Result<u32, PuzzleErr> {
// Parse modules from input.
let mut modules = parse_input(input)?;
// Tracker for the total number of pulses.
let mut pulse_counter = PulseCounter::new();
// Perform button presses.
for _ in 0..n_button_presses {
let mut pulses = VecDeque::from_iter([PulseMsg {
from: "button".to_string(),
to: "broadcaster".to_string(),
pulse: Pulse::Low,
}]);
pulse_counter.low += 1;
while !pulses.is_empty() {
let pulse = pulses.pop_front().unwrap();
log::trace!("PULSE: {:?}", pulse);
if let Some(response) = match modules.get_mut(&pulse.to) {
Some(Module::B(b)) => b.receive(&pulse),
Some(Module::C(c)) => c.receive(&pulse),
Some(Module::F(f)) => f.receive(&pulse),
Some(Module::O(o)) => o.receive(&pulse),
None => None,
} {
log::trace!("Received {} responses.", response.len());
response.into_iter().for_each(|r| {
log::trace!("RESPONSE: {:?}", r);
pulse_counter.track(&r);
pulses.push_back(r);
});
}
}
}
log::info!(
"Final counts: {} low, {} high",
pulse_counter.low,
pulse_counter.high
);
Ok(pulse_counter.low * pulse_counter.high)
}
pub fn puzzle_2(input: &str) -> Result<u64, PuzzleErr> {
// Parse modules from input.
let mut modules = parse_input(input)?;
// Get the input module for "rx" module.
let rx_input = modules
.values()
.filter(|m| match m {
Module::C(c) => c.receivers.contains(&"rx".to_string()),
_ => false,
})
.collect::<Vec<_>>()
.first()
.cloned()
.unwrap();
log::info!("'rx' module input: {:?}", rx_input);
// Dict for the memory inputs of the "rx" input.
// Will count how many button presses until set "HIGH".
let rx_input_inputs = match rx_input {
Module::C(c) => Ok(c.memory.keys().cloned().collect::<HashSet<_>>()),
_ => Err(PuzzleErr::Part2ExpectationViolated),
}?;
log::info!("inputs to 'rx' input: {:?}", rx_input_inputs);
let mut rx_input_presses = HashMap::<String, u32>::new();
for num_presses in 1..u32::MAX {
let mut pulses = VecDeque::from_iter([PulseMsg {
from: "button".to_string(),
to: "broadcaster".to_string(),
pulse: Pulse::Low,
}]);
while !pulses.is_empty() {
let pulse = pulses.pop_front().unwrap();
// Record num. button presses for HIGH pulses from inputs to input of "rx".
if (pulse.pulse == Pulse::High)
& rx_input_inputs.contains(&pulse.from)
& !rx_input_presses.contains_key(&pulse.from)
{
log::info!(
"Recording {} presses for module {}",
num_presses,
pulse.from
);
rx_input_presses.insert(pulse.from.clone(), num_presses);
}
// All inputs to the input for "rx" found a HIGH pulse.
if rx_input_inputs
.iter()
.all(|i| rx_input_presses.contains_key(i))
{
log::info!(
"Found button presses for all 'rx' input inputs: {:?}.",
rx_input_presses
);
return Ok(math_utils::lcm(
rx_input_presses
.values()
.map(|x| *x as u64)
.collect::<Vec<_>>(),
));
}
// Send pulse and add responses to queue.
if let Some(response) = match modules.get_mut(&pulse.to) {
Some(Module::B(b)) => b.receive(&pulse),
Some(Module::C(c)) => c.receive(&pulse),
Some(Module::F(f)) => f.receive(&pulse),
Some(Module::O(o)) => o.receive(&pulse),
None => None,
} {
response.into_iter().for_each(|r| pulses.push_back(r));
}
}
}
unreachable!();
}
pub fn main(data_dir: &str) {
println!("Day 20: Pulse Propagation");
let data = load(data_dir, 20, None);
// Puzzle 1.
let answer_1 = puzzle_1(&data, 1000);
match answer_1 {
Ok(x) => println!(" Puzzle 1: {}", x),
Err(e) => panic!("No solution to puzzle 1: {}.", e),
}
assert_eq!(answer_1, Ok(944750144));
// Puzzle 2.
let answer_2 = puzzle_2(&data);
match answer_2 {
Ok(x) => println!(" Puzzle 2: {}", x),
Err(e) => panic!("No solution to puzzle 2: {}", e),
}
assert_eq!(answer_2, Ok(222718819437131))
}