day20: problem 2 solution - needed a hint
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83
20/Cargo.lock
generated
83
20/Cargo.lock
generated
@ -11,11 +11,18 @@ dependencies = [
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"memchr",
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]
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[[package]]
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name = "autocfg"
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version = "1.1.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
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[[package]]
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name = "day20"
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version = "0.1.0"
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dependencies = [
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"lazy-regex",
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"num",
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]
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[[package]]
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@ -47,6 +54,82 @@ version = "2.6.4"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"
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[[package]]
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name = "num"
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version = "0.4.1"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "b05180d69e3da0e530ba2a1dae5110317e49e3b7f3d41be227dc5f92e49ee7af"
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dependencies = [
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"num-bigint",
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"num-complex",
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"num-integer",
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"num-iter",
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"num-rational",
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"num-traits",
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]
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[[package]]
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name = "num-bigint"
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version = "0.4.4"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "608e7659b5c3d7cba262d894801b9ec9d00de989e8a82bd4bef91d08da45cdc0"
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dependencies = [
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"autocfg",
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"num-integer",
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"num-traits",
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]
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[[package]]
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name = "num-complex"
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version = "0.4.4"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "1ba157ca0885411de85d6ca030ba7e2a83a28636056c7c699b07c8b6f7383214"
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dependencies = [
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"num-traits",
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]
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[[package]]
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name = "num-integer"
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version = "0.1.45"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "225d3389fb3509a24c93f5c29eb6bde2586b98d9f016636dff58d7c6f7569cd9"
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dependencies = [
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"autocfg",
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"num-traits",
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]
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[[package]]
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name = "num-iter"
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version = "0.1.43"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "7d03e6c028c5dc5cac6e2dec0efda81fc887605bb3d884578bb6d6bf7514e252"
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dependencies = [
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"autocfg",
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"num-integer",
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"num-traits",
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]
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[[package]]
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name = "num-rational"
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version = "0.4.1"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "0638a1c9d0a3c0914158145bc76cff373a75a627e6ecbfb71cbe6f453a5a19b0"
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dependencies = [
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"autocfg",
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"num-bigint",
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"num-integer",
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"num-traits",
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]
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[[package]]
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name = "num-traits"
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version = "0.2.17"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "39e3200413f237f41ab11ad6d161bc7239c84dcb631773ccd7de3dfe4b5c267c"
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dependencies = [
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"autocfg",
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]
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[[package]]
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name = "once_cell"
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version = "1.19.0"
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@ -7,3 +7,4 @@ edition = "2021"
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[dependencies]
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lazy-regex = "3.1.0"
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num = "0.4.1"
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118
20/src/main.rs
118
20/src/main.rs
@ -1,10 +1,12 @@
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use std::collections::{BinaryHeap, HashMap, VecDeque};
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use std::fmt::Display;
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use std::fs::File;
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use std::hash::{Hash, Hasher};
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use std::io::{BufRead, BufReader, Lines};
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use std::time::Instant;
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use lazy_regex::lazy_regex;
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use num::integer::lcm;
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// BOILERPLATE
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type InputIter = Lines<BufReader<File>>;
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@ -31,7 +33,7 @@ fn main() {
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const MODULE_PATTERN: lazy_regex::Lazy<lazy_regex::Regex> = lazy_regex!("^([%&]?)([a-z]+) -> ([a-z, ]+)$");
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#[derive(Debug, PartialEq, Eq, Clone, Copy)]
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#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash)]
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enum PulseType {
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Low,
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High,
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@ -79,7 +81,15 @@ struct Module {
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inputs: Vec<String>,
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outputs: Vec<String>,
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on: bool,
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last_input_states: HashMap<String, PulseType>,
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last_input_states: Vec<PulseType>,
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}
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impl Hash for Module {
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fn hash<H: Hasher>(&self, state: &mut H) {
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// the only states that change are 'on' and 'last_input_states', the rest are constant once created
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self.on.hash(state);
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self.last_input_states.hash(state);
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}
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}
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impl Module {
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@ -90,18 +100,19 @@ impl Module {
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inputs: Vec::new(),
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outputs: Vec::new(),
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on: false,
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last_input_states: HashMap::new(),
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last_input_states: Vec::new(),
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}
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}
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fn source_idx(&self, name: &str) -> usize {
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self.inputs.iter().position(|in_name| in_name == name).unwrap()
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}
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fn with_kind(name: String, kind: ModuleKind) -> Self {
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let mut m = Self::new(name);
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m.kind = Some(kind);
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m
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}
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fn and_destinations(mut self, destinations: &str) -> Self {
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println!("{} destinations: {}", self.name, destinations);
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for dest in destinations.split(", ") {
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println!(" {}", dest);
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self.outputs.push(dest.into());
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}
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self
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@ -110,15 +121,29 @@ impl Module {
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self.add_source(source);
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self
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}
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fn add_source(&mut self, source: String) {
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self.inputs.push(source.clone());
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self.last_input_states.insert(source, PulseType::Low);
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fn add_source(&mut self, source: String) {
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self.inputs.push(source);
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self.last_input_states.push(PulseType::Low);
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}
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fn reset(&mut self) {
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// relevant state is on and last_input_states
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self.on = false;
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for input in &mut self.last_input_states {
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*input = PulseType::Low;
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}
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}
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fn state_space(&self) -> u128 {
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match self.kind {
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Some(ModuleKind::Broadcast) | Some(ModuleKind::Button) => 1,
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Some(ModuleKind::FlipFlop) => 2,
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Some(ModuleKind::Conjunction) => 1 << self.last_input_states.len(), // 2^n
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None => 1
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}
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}
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}
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impl From<&str> for Module {
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fn from(s: &str) -> Self {
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println!("s: {}", s);
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let Some(re_result) = MODULE_PATTERN.captures(s) else {
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panic!("unparseable module: {}", s);
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};
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@ -166,7 +191,7 @@ struct Machine {
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modules: HashMap<String, Module>,
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work_queue: BinaryHeap<Job>,
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count_low: u64,
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count_high: u64
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count_high: u64,
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}
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impl<T: BufRead> From<Lines<T>> for Machine {
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@ -199,7 +224,8 @@ impl<T: BufRead> From<Lines<T>> for Machine {
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Machine {
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modules,
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work_queue: BinaryHeap::new(),
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count_low: 0, count_high: 0
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count_low: 0,
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count_high: 0,
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}
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}
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}
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@ -227,16 +253,10 @@ impl Machine {
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}
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},
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Some(ModuleKind::Conjunction) => {
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self.modules
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.get_mut(target)
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.unwrap()
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.last_input_states
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.insert(from.to_owned(), signal);
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if self.modules[target]
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.last_input_states
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.values()
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.all(|state| *state == PulseType::High)
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{
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let target_m = self.modules.get_mut(target).unwrap();
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let source_idx = target_m.source_idx(from);
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target_m.last_input_states[source_idx] = signal;
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if target_m.last_input_states.iter().all(|state| *state == PulseType::High) {
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self.send_all_outputs(PulseType::Low, target, priority)
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} else {
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self.send_all_outputs(PulseType::High, target, priority)
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@ -260,13 +280,34 @@ impl Machine {
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}
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}
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}
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// the number of cycles it took until the target sends a low pulse, or None if the target node sent no low pulses but the job finished
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fn time_to_state(&mut self, goal:&str, state: PulseType) -> Option<u64> {
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while let Some(job) = self.work_queue.pop() {
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if job.from == goal && job.signal == state {
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return Some(self.count_high + self.count_low);
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}
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for target in job.targets {
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self.send_pulse(job.signal, &target, &job.from, job.priority);
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}
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}
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None
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}
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fn reset(&mut self) {
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for (_name, m) in &mut self.modules {
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m.reset();
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}
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self.count_low = 0;
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self.count_high = 0;
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}
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fn state_space(&self) -> u128 {
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self.modules.values().map(|m| m.state_space()).product()
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}
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}
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// PROBLEM 1 solution
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const PROBLEM1_ITERATIONS: usize = 1000;
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fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
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let mut machine = Machine::from(input);
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println!("{:?}", machine);
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for _ in 0..PROBLEM1_ITERATIONS {
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machine.press_button();
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machine.run();
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@ -275,8 +316,31 @@ fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
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}
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// PROBLEM 2 solution
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fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
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0
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fn problem2<T: BufRead>(input: Lines<T>) -> u128 {
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let mut machine = Machine::from(input);
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println!("STATES: {}", machine.state_space());
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// Find the rx module and look at its parent(s)
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let rx = &machine.modules["rx"];
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// my input has a single conjunction as parent, todo implement other possibilities
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let con = &machine.modules[&rx.inputs[0]];
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// for each input, find how long it takes for it to be High, so the conjunction sends a low to rx
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let mut cycles: Vec<_> = Vec::new();
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for input in con.inputs.clone() {
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print!("searching distance to {}...", input);
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machine.reset();
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let mut button_count = 0;
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loop {
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machine.press_button();
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button_count += 1;
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if let Some(distance) = machine.time_to_state(&input, PulseType::High) {
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println!("got {} pulses, {} button presses", distance, button_count);
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cycles.push(button_count as u128);
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break;
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}
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}
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}
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cycles.iter().fold(1, |accum, cycle| lcm(accum, *cycle))
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}
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#[cfg(test)]
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@ -295,10 +359,4 @@ mod tests {
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let c = Cursor::new(EXAMPLE);
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assert_eq!(problem1(c.lines()), 11687500);
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}
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#[test]
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fn problem2_example() {
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let c = Cursor::new(EXAMPLE);
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assert_eq!(problem2(c.lines()), 0);
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}
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}
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