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add problem 06

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timeshifter
2026-07-13 21:29:03 +02:00
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commit 924964fcfb
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problem06/Cargo.lock
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problem06/Cargo.toml
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[package]
name = "problem06"
version = "0.1.0"
edition = "2024"
[dependencies]
tokio = { version = "1", features = ["full"] }
anyhow = "1"
itertools = "0"
problem06/src/main.rs
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use std::collections::{HashMap, HashSet};
use std::sync::{Arc, Mutex, MutexGuard};
use anyhow::{Result, ensure};
use itertools::Itertools;
use tokio::io::AsyncWriteExt;
use tokio::sync::broadcast::{self, Receiver, Sender};
use tokio::{
io::AsyncReadExt,
net::{TcpListener, TcpStream},
};
type PlateLog = HashMap<String, Vec<(Camera, u32)>>;
type TicketLog = HashSet<(String, usize)>;
#[tokio::main]
async fn main() -> Result<()> {
let listener = TcpListener::bind("0.0.0.0:10000").await?;
let plates = Arc::new(Mutex::new(HashMap::new()));
let days_with_issued_tickets = Arc::new(Mutex::new(TicketLog::new()));
let ticket_queue = Arc::new(Mutex::new(vec![]));
let (tx, _) = broadcast::channel(100_000);
loop {
let (socket, _) = listener.accept().await?;
let this_plates = plates.clone();
let this_tx = tx.clone();
let this_queue = ticket_queue.clone();
let this_days_tickets = days_with_issued_tickets.clone();
tokio::spawn(async move {
match handle_connection(socket, this_plates, this_queue, this_days_tickets, this_tx)
.await
{
Ok(()) => (),
Err(e) => {
dbg!(e);
}
}
});
}
}
async fn handle_connection(
mut socket: TcpStream,
plates: Arc<Mutex<PlateLog>>,
ticket_queue: Arc<Mutex<Vec<Ticket>>>,
days_with_issued_tickets: Arc<Mutex<TicketLog>>,
tx: Sender<ChannelMessage>,
) -> Result<()> {
let (mut reader, mut writer) = socket.split();
let mut heartbeat_interval = None;
let mut timer = tokio::time::interval(std::time::Duration::from_hours(100));
timer.tick().await;
loop {
tokio::select! {
_ = timer.tick() => {
writer.write_all(&[0x41]).await?;
}
byte = reader.read_u8() => {
match byte? {
0x40 => {
if heartbeat_interval.is_some() {
send_error_message(&mut writer, "multiple heartbeat requests").await?;
return Ok(());
}
let interval = reader.read_u32().await?;
heartbeat_interval = Some(interval);
if interval > 0 {
timer = tokio::time::interval(std::time::Duration::from_millis(
100.max((interval as u64 * 100) - 100),
));
}
}
0x80 => {
camera_main_loop(reader, writer, plates, ticket_queue, timer, heartbeat_interval, tx).await?;
return Ok(());
}
0x81 => {
let rx = tx.subscribe();
dispatcher_main_loop(reader, writer, ticket_queue, days_with_issued_tickets, timer, heartbeat_interval, rx)
.await?;
return Ok(());
}
other => {
return send_error_message(
&mut writer,
&format!("initialized with wrong message type 0x{other:x}"),
)
.await;
}
};
}
}
}
}
async fn dispatcher_main_loop(
mut reader: tokio::net::tcp::ReadHalf<'_>,
mut writer: tokio::net::tcp::WriteHalf<'_>,
ticket_queue: Arc<Mutex<Vec<Ticket>>>,
days_with_issued_tickets: Arc<Mutex<TicketLog>>,
mut timer: tokio::time::Interval,
mut heartbeat_interval: Option<u32>,
mut rx: Receiver<ChannelMessage>,
) -> Result<()> {
let num_roads = reader.read_u8().await?;
let mut roads = vec![];
for _ in 0..num_roads {
roads.push(reader.read_u16().await?);
}
work_ticket_queue(
&roads,
&mut writer,
&ticket_queue,
&days_with_issued_tickets,
)
.await?;
loop {
tokio::select! {
_ = timer.tick() => {
writer.write_all(&[0x41]).await?;
}
_ = rx.recv() => {
work_ticket_queue(&roads, &mut writer, &ticket_queue, &days_with_issued_tickets).await?;
}
byte = reader.read_u8() => {
match byte? {
0x40 => {
if heartbeat_interval.is_some() {
send_error_message(&mut writer, "multiple heartbeat requests").await?;
return Ok(());
}
heartbeat_interval = Some(reader.read_u32().await?);
if let Some(interval) = heartbeat_interval
&& interval > 0
{
timer = tokio::time::interval(std::time::Duration::from_millis(
100.max((interval * 100) as u64 - 100),
));
}
}
_ => {
return send_error_message(&mut writer, "received wrong message type").await;
}
}
}
}
}
}
async fn work_ticket_queue(
roads: &[u16],
writer: &mut tokio::net::tcp::WriteHalf<'_>,
ticket_queue: &Arc<Mutex<Vec<Ticket>>>,
days_with_issued_tickets: &Arc<Mutex<TicketLog>>,
) -> Result<()> {
let messages = generate_ticket_messages(ticket_queue, roads, days_with_issued_tickets).await?;
for message in messages {
writer.write_all(&message).await?;
}
Ok(())
}
async fn generate_ticket_messages(
queue: &Arc<Mutex<Vec<Ticket>>>,
roads: &[u16],
days_with_issued_tickets: &Arc<Mutex<TicketLog>>,
) -> Result<Vec<Vec<u8>>> {
let mut queue = queue.lock().unwrap();
let mut days = days_with_issued_tickets.lock().unwrap();
let own_tickets = queue
.iter()
.positions(|ticket| roads.contains(&ticket.road));
let mut messages = vec![];
let mut to_remove = vec![];
for idx in own_tickets {
let ticket = queue.get(idx).unwrap();
to_remove.push(idx);
let day1 = timestamp_to_day(ticket.timestamp1);
let day2 = timestamp_to_day(ticket.timestamp2);
let key1 = (ticket.plate.clone(), day1);
let key2 = (ticket.plate.clone(), day2);
if days.contains(&key1) || days.contains(&key2) {
continue;
}
days.insert(key1);
days.insert(key2);
let to_wire = ticket_to_vec_u8(ticket);
messages.push(to_wire);
}
to_remove.sort();
for idx in to_remove.iter().rev() {
queue.remove(*idx);
}
Ok(messages)
}
fn timestamp_to_day(timestamp: u32) -> usize {
(timestamp / 86400) as _
}
fn ticket_to_vec_u8(ticket: &Ticket) -> Vec<u8> {
let mut to_wire = vec![0x21];
// plate
to_wire.push(ticket.plate.len() as u8);
for byte in ticket.plate.as_bytes() {
to_wire.push(*byte);
}
// road
for byte in ticket.road.to_be_bytes() {
to_wire.push(byte);
}
// mile 1, timestamp 1
for byte in ticket.mile1.to_be_bytes() {
to_wire.push(byte);
}
for byte in ticket.timestamp1.to_be_bytes() {
to_wire.push(byte);
}
// mile 2, timestamp 2
for byte in ticket.mile2.to_be_bytes() {
to_wire.push(byte);
}
for byte in ticket.timestamp2.to_be_bytes() {
to_wire.push(byte);
}
// speed
for byte in ticket.speed.to_be_bytes() {
to_wire.push(byte);
}
to_wire
}
async fn camera_main_loop(
mut reader: tokio::net::tcp::ReadHalf<'_>,
mut writer: tokio::net::tcp::WriteHalf<'_>,
plates: Arc<Mutex<PlateLog>>,
ticket_queue: Arc<Mutex<Vec<Ticket>>>,
mut timer: tokio::time::Interval,
mut heartbeat_interval: Option<u32>,
tx: Sender<ChannelMessage>,
) -> Result<()> {
let myself = Camera {
road: reader.read_u16().await?,
mile: reader.read_u16().await?,
limit: reader.read_u16().await?,
};
loop {
tokio::select! {
_ = timer.tick() => {
writer.write_all(&[0x41]).await?;
}
byte = reader.read_u8() => {
match byte? {
0x20 => {
let plate = read_string(&mut reader).await?;
let timestamp = reader.read_u32().await?;
{
let mut this_plates = plates.lock().unwrap();
this_plates
.entry(plate.clone())
.and_modify(|v| v.push((myself.clone(), timestamp)))
.or_insert(vec![(myself.clone(), timestamp)]);
for ticket in find_possible_tickets(this_plates, &myself, plate, timestamp)
{
ticket_queue.lock().unwrap().push(ticket);
let _ = tx.send(ChannelMessage::TicketIssued);
}
}
}
0x40 => {
if heartbeat_interval.is_some() {
send_error_message(&mut writer, "multiple heartbeat requests").await?;
return Ok(());
}
heartbeat_interval = Some(reader.read_u32().await?);
if let Some(interval) = heartbeat_interval
&& interval > 0
{
timer = tokio::time::interval(std::time::Duration::from_millis(
100.max((interval * 100) as u64 - 100),
));
}
}
_ => {
return send_error_message(&mut writer, "received wrong message type").await;
}
}
}
}
}
}
fn find_possible_tickets(
plates: MutexGuard<'_, PlateLog>,
this_camera: &Camera,
this_plate: String,
this_timestamp: u32,
) -> Vec<Ticket> {
let relevant: Vec<_> = plates
.iter()
.filter(|(plate, _)| **plate == this_plate)
.flat_map(|(_, camera_timestamp_map)| camera_timestamp_map)
.filter(|(camera, _)| camera.road == this_camera.road)
.collect();
let violations = relevant
.iter()
.combinations(2)
.filter(|data| {
data.iter()
.any(|(_, timestamp)| *timestamp == this_timestamp)
})
.map(|data| (data.clone(), calculate_speed(data).unwrap()))
.filter(|(_, speed)| *speed > this_camera.limit * 100);
let mut result = vec![];
for violation in violations {
let (camera_timestamp_map, speed) = violation;
let ticket = Ticket::new(
this_plate.clone(),
this_camera.road,
camera_timestamp_map[0].0.mile,
camera_timestamp_map[0].1,
camera_timestamp_map[1].0.mile,
camera_timestamp_map[1].1,
speed,
);
result.push(ticket);
}
result
}
fn calculate_speed(timestamps: Vec<&&(Camera, u32)>) -> Option<u16> {
let mut data = timestamps.clone();
data.sort_by_key(|(_, time)| time);
let dt = (data[1].1 - data[0].1) as u64;
let ds = (data[1].0.mile as i64 - data[0].0.mile as i64).unsigned_abs();
if dt == 0 {
return None;
}
Some(((ds * 3600 * 100) / dt) as _)
}
async fn send_error_message(
writer: &mut tokio::net::tcp::WriteHalf<'_>,
message: &str,
) -> Result<()> {
let mut to_wire = vec![0x10];
ensure!(message.len() <= 255, "message too long");
to_wire.push(message.len() as u8);
for byte in message.as_bytes() {
to_wire.push(*byte);
}
writer.write_all(&to_wire).await?;
Ok(())
}
async fn read_string(r: &mut (impl AsyncReadExt + Unpin)) -> Result<String> {
let len = r.read_u8().await?;
let mut buf = vec![0u8; len as usize];
r.read_exact(&mut buf).await?;
Ok(String::from_utf8(buf)?)
}
#[derive(Clone, Debug)]
struct Camera {
road: u16,
mile: u16,
limit: u16,
}
#[derive(Clone, Debug)]
struct Ticket {
plate: String,
road: u16,
mile1: u16,
timestamp1: u32,
mile2: u16,
timestamp2: u32,
speed: u16,
}
impl Ticket {
fn new(
plate: String,
road: u16,
mut mile1: u16,
mut timestamp1: u32,
mut mile2: u16,
mut timestamp2: u32,
speed: u16,
) -> Self {
if timestamp2 < timestamp1 {
(mile1, mile2) = (mile2, mile1);
(timestamp1, timestamp2) = (timestamp2, timestamp1);
}
Self {
plate,
road,
mile1,
timestamp1,
mile2,
timestamp2,
speed,
}
}
}
#[derive(Clone, Debug)]
#[non_exhaustive]
enum ChannelMessage {
TicketIssued,
}