aoc23/src/bin/day8.rs

#![forbid(elided_lifetimes_in_paths)]

use aoc23::read;
use chumsky::prelude::*;
use std::{
	collections::{HashMap, HashSet},
	sync::{
		atomic::{AtomicBool, Ordering},
		Mutex
	},
	thread,
	time::Duration
};

#[derive(Clone, Copy, Debug)]
enum Instruction {
	Left,
	Right
}

impl Instruction {
	fn parser() -> impl Parser<char, Self, Error = Simple<char>> {
		choice((
			just('L').map(|_| Self::Left),
			just('R').map(|_| Self::Right)
		))
	}
}

#[derive(Clone, Debug)]
struct Node {
	left: String,
	right: String
}

fn parse_node_name() -> impl Parser<char, String, Error = Simple<char>> {
	none_of([',', ')', ' '])
		.repeated()
		.at_least(1)
		.map(|chars| chars.into_iter().collect())
}

impl Node {
	fn parser() -> impl Parser<char, Self, Error = Simple<char>> {
		just("(")
			.ignore_then(parse_node_name())
			.then_ignore(just(", "))
			.then(parse_node_name())
			.then_ignore(just(")"))
			.map(|(left, right)| Self { left, right })
	}
}

#[derive(Clone, Debug)]
struct Network {
	nodes: HashMap<String, Node>
}

impl Network {
	fn parser() -> impl Parser<char, Self, Error = Simple<char>> {
		parse_node_name()
			.then_ignore(just(" = "))
			.then(Node::parser())
			.then_ignore(just("\n"))
			.repeated()
			.map(|nodes| Self {
				nodes: nodes.into_iter().collect()
			})
	}

	fn node(&self, node: &str) -> &Node {
		self.nodes
			.get(node)
			.unwrap_or_else(|| panic!("Failed to get node {node:?}"))
	}

	fn left(&self, node: &str) -> &str {
		&self.node(node).left
	}

	fn right(&self, node: &str) -> &str {
		&self.node(node).right
	}
}

fn parser() -> impl Parser<char, (Vec<Instruction>, Network), Error = Simple<char>> {
	Instruction::parser()
		.repeated()
		.at_least(1)
		.then_ignore(just("\n\n"))
		.then(Network::parser())
		.then_ignore(end())
}

static STOP: AtomicBool = AtomicBool::new(false);
static mut RESULTS: Vec<Mutex<Vec<usize>>> = Vec::new();

fn main() -> anyhow::Result<()> {
	let (instructions, network) = read("inputs/day8.txt", parser())?;

	// let mut curr_node = "AAA";
	// let mut i = 0;
	// let mut steps = 0;
	// while curr_node != "ZZZ" {
	// 	curr_node = match instructions[i] {
	// 		Instruction::Left => network.left(curr_node),
	// 		Instruction::Right => network.right(curr_node)
	// 	};
	// 	i = (i + 1) % instructions.len();
	// 	steps += 1;
	// }
	// println!("{steps}");

	let curr_nodes: HashSet<&str> = network
		.nodes
		.keys()
		.map(|node| node.as_str())
		.filter(|node| node.ends_with('A'))
		.collect();
	dbg!(curr_nodes.len());

	for (thread_index, node) in curr_nodes
		.iter()
		.map(|node| String::from(*node))
		.enumerate()
	{
		unsafe {
			RESULTS.push(Mutex::new(Vec::new()));
		}
		let network = network.clone();
		let instructions = instructions.clone();
		thread::spawn(move || {
			let mut curr_node = node.as_str();
			let mut i = 0;
			let mut steps = 0;
			while !STOP.load(Ordering::Relaxed) {
				curr_node = match instructions[i] {
					Instruction::Left => network.left(curr_node),
					Instruction::Right => network.right(curr_node)
				};
				i = (i + 1) % instructions.len();
				steps += 1;
				if steps % 1_000_000 == 0 {
					dbg!(steps);
				}
				if curr_node.ends_with('Z') {
					unsafe {
						RESULTS[thread_index].lock().unwrap().push(steps);
					}
				}
			}
		});
	}
	'outer: loop {
		thread::sleep(Duration::from_secs(1));
		unsafe {
			let res0 = RESULTS[0].lock().unwrap();
			'i: for i in 0 .. res0.len() {
				't: for t in 1 .. RESULTS.len() {
					let rest = RESULTS[t].lock().unwrap();
					for j in 0 .. rest.len() {
						if res0[i] == rest[j] {
							continue 't;
						}
					}
					continue 'i;
				}
				println!("{}", res0[i]);
				STOP.store(true, Ordering::Relaxed);
				break 'outer;
			}
		}
	}

	// let mut i = 0;
	// let mut steps = 0;
	// while curr_nodes.iter().any(|node| !node.ends_with('Z')) {
	// 	curr_nodes = curr_nodes
	// 		.into_iter()
	// 		.map(|node| match instructions[i] {
	// 			Instruction::Left => network.left(node),
	// 			Instruction::Right => network.right(node)
	// 		})
	// 		.collect();
	// 	i = (i + 1) % instructions.len();
	// 	steps += 1;
	// 	if steps % 10000 == 0 {
	// 		dbg!(steps);
	// 	}
	// }
	// println!("{steps}");

	Ok(())
}