adventofcode2023/day20/src/main_sane.rs

use std::cmp;
use std::collections::{HashMap, VecDeque};
use std::fs::read_to_string;
use std::time::Instant;
use num::integer::lcm;

struct Pulse {
    src: u16,
    dest: u16,
    high: bool,
}

enum ModuleKind {
    Broadcast,
    FlipFlop(bool),
    Conjunction(Vec<bool>),
}

struct Module {
    inputs: Vec<u16>,
    outputs: Vec<u16>,
    id: u16,
    kind: ModuleKind,
}

impl Module {
    fn new(id: u16, kind: ModuleKind) -> Module {
        Module {
            inputs: vec![],
            outputs: vec![],
            id,
            kind,
        }
    }

    fn new_broadcast(id: u16) -> Module {
        Module::new(id, ModuleKind::Broadcast)
    }

    fn new_flipflop(id: u16) -> Module {
        Module::new(id, ModuleKind::FlipFlop(false))
    }

    fn new_conjunction(id: u16) -> Module {
        Module::new(id, ModuleKind::Conjunction(vec![]))
    }

    fn add_input(&mut self, id: u16) {
        self.inputs.push(id);
        match self.kind {
            ModuleKind::Conjunction(ref mut memory) => {
                memory.push(false);
            }
            _ => {}
        }
    }

    fn add_output(&mut self, id: u16) {
        self.outputs.push(id);
    }

    fn handle_pulse(&mut self, pulse: Pulse, queue: &mut VecDeque<Pulse>) {
        match self.kind {
            ModuleKind::Broadcast => {
                queue.extend(self.outputs.iter().map(
                    |&id| Pulse { src: self.id, dest: id, high: pulse.high }));
            }
            ModuleKind::FlipFlop(ref mut on) => {
                if !pulse.high {
                    *on = !*on;
                    queue.extend(self.outputs.iter().map(
                        |&id| Pulse { src: self.id, dest: id, high: *on }));
                }
            }
            ModuleKind::Conjunction(ref mut memory) => {
                if let Some(pos) = self.inputs.iter().position(|&id| id == pulse.src) {
                    memory[pos] = pulse.high;
                    let out_high = !memory.iter().all(|&v| v);
                    queue.extend(self.outputs.iter().map(
                        |&id| Pulse { src: self.id, dest: id, high: out_high }));
                }
            }
        }
    }
}

fn encode_module_name(name: &str) -> u16 {
    let bytes = &name.as_bytes()[0..cmp::min(name.as_bytes().len(), 3)];
    let mut acc = 0u16;
    for &c in bytes {
        acc = acc * 26 + (c - b'a') as u16;
    }
    acc
}

fn main() {
    let time_start = Instant::now();
    let input_str = read_to_string("input.txt").unwrap();
    let time_start_no_io = Instant::now();
    let mut modules: HashMap<u16, Module> = HashMap::new();
    // let rx_id = encode_module_name("rx");
    // modules.insert(rx_id, Module::new_flipflop(rx_id));
    for line in input_str.lines() {
        let mut split_whitespace = line.split_whitespace();
        let name = split_whitespace.next().unwrap();
        let new_module: Module;
        let id = encode_module_name(&name[1..]);
        match name.as_bytes()[0] {
            b'%' => new_module = Module::new_flipflop(id),
            b'&' => new_module = Module::new_conjunction(id),
            _ => new_module = Module::new_broadcast(id)
        }
        modules.insert(id, new_module);
    }
    for line in input_str.lines() {
        let mut split = line.split([' ', ',']).
            filter(|&v| !v.is_empty());
        let name = split.next().unwrap();
        let in_id = encode_module_name(&name[1..]);
        split.next();
        while let Some(name) = split.next() {
            let id = encode_module_name(name);
            modules.get_mut(&in_id).unwrap().add_output(id);
            match modules.get_mut(&id) {
                None => {}
                Some(in_module) => {
                    in_module.add_input(in_id);
                }
            }
        }
    }
    // Part 1
    let broadcast_id = encode_module_name("roadcast");
    let mut low_pulses = 0u64;
    let mut high_pulses = 0u64;
    let mut queue: VecDeque<Pulse> = VecDeque::new();
    for _ in 0..1000 {
        let mut low_pulses_step = 0;
        let mut high_pulses_step = 0;
        queue.push_back(Pulse { src: u16::MAX, dest: broadcast_id, high: false });
        while !queue.is_empty() {
            let pulse = queue.pop_front().unwrap();
            match pulse.high {
                true => high_pulses_step += 1,
                false => low_pulses_step += 1
            }
            match modules.get_mut(&pulse.dest) {
                None => {}
                Some(module) => {
                    module.handle_pulse(pulse, &mut queue);
                }
            }
        }
        low_pulses += low_pulses_step;
        high_pulses += high_pulses_step;
    }
    let result1 = low_pulses * high_pulses;
    // Part 2
    // Use the knowledge of the network, that it is that broadcast drives a series of counters
    let mut counter_periods: Vec<u64> = vec![];
    for &node in &modules.get(&broadcast_id).unwrap().outputs {
        let mut period = 0u16;
        let mut current_node = node;
        let mut bits = 0;
        loop {
            bits += 1;
            let mut next_id = current_node;
            period >>= 1;
            let outputs = &modules.get(&current_node).unwrap().outputs;
            for &output_id in outputs {
                match modules.get(&output_id).unwrap().kind {
                    ModuleKind::Conjunction(_) => period |= 0x8000,
                    _ => next_id = output_id
                }
            }
            if next_id == current_node {
                break;
            } else {
                current_node = next_id;
            }
        }
        period >>= 16 - bits;
        counter_periods.push(period as u64);
    }
    let result2 = counter_periods.iter().fold(1u64, |acc, &v| lcm(acc, v));
    let elapsed = time_start.elapsed().as_micros();
    let elapsed_no_io = time_start_no_io.elapsed().as_micros();
    println!("Time: {}us", elapsed);
    println!("Time without file i/o: {}us", elapsed_no_io);
    println!("Result1: {}", result1);
    println!("Result2: {}", result2);
}