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use std::env;
use std::io::BufReader;
use std::io::BufRead;
use std::fs::File;
use std::process;
use std::collections::{HashMap, HashSet};
use std::io::{stdin, stdout, Write};
type Track = char;
#[derive(Copy)]
struct Cart {
dir: (i32, i32),
next_rot: i32,
id: u32
}
impl Clone for Cart {
fn clone(&self) -> Cart { *self }
}
type Tracks = HashMap<(usize, usize), Track>;
type Carts = HashMap<(usize, usize), Cart>;
impl Cart {
fn char(&self) -> char {
match self.dir {
(1, 0) => '>',
(-1, 0) => '<',
(0, 1) => 'v',
(0, -1) => '^',
_ => panic!("Invalid dir")
}
}
}
fn is_track(ch: char) -> bool {
ch == '/' || ch == '\\' || ch == '+'
}
fn track_at(tracks: &Tracks, x: usize, y: usize) -> bool {
tracks.contains_key(&(x, y))
}
fn is_cart(ch: char) -> bool {
ch == '<' || ch == '>' || ch == '^' || ch == 'v'
}
fn cart_at(carts: &Carts, x: usize, y: usize) -> bool {
carts.contains_key(&(x, y))
}
fn cart_dir(ch: char) -> (i32, i32) {
match ch {
'>' => (1, 0),
'<' => (-1, 0),
'^' => (0, -1),
'v' => (0, 1),
_ => panic!("Not a cart")
}
}
fn rot_cart(cart: &Cart, curve: char) -> (i32, i32) {
let dir = cart.dir;
if curve == '/' {
match dir {
(1, 0) => (0, -1),
(-1, 0) => (0, 1),
(0, -1) => (1, 0),
(0, 1) => (-1, 0),
_ => panic!("Not a correct direction")
}
}
else if curve == '\\' {
match dir {
(1, 0) => (0, 1),
(-1, 0) => (0, -1),
(0, -1) => (-1, 0),
(0, 1) => (1, 0),
_ => panic!("Not a correct direction")
}
}
else if curve == '+' {
match cart.next_rot {
-1 => match dir {
(1, 0) => (0, -1),
(0, 1) => (1, 0),
(-1, 0) => (0, 1),
(0, -1) => (-1, 0),
_ => panic!("Not a correct direction")
},
0 => dir,
1 => match dir {
(1, 0) => (0, 1),
(0, 1) => (-1, 0),
(-1, 0) => (0, -1),
(0, -1) => (1, 0),
_ => panic!("Not a correct direction")
},
_ => panic!("Not a correct next_rot")
}
} else {
panic!("Not a valid curve");
}
}
fn visualize(tracks: &Tracks, carts: &Carts, my: usize, mx: usize) {
for y in 0..my {
for x in 0..mx {
if cart_at(carts, x, y) {
print!("{}", carts[&(x, y)].char());
}
else if track_at(&tracks, x, y) {
print!("{}", tracks[&(x, y)]);
}
else {
print!(" ");
}
}
print!("\n");
}
let mut s = String::new();
let _ = stdout().flush();
stdin().read_line(&mut s).expect("Did not enter a correct string");
}
fn main() {
let args: Vec<String> = env::args().collect();
if args.len() != 2 {
println!("Wrong number of arguments. Provide a file name and worker count.");
process::exit(1);
}
let filename = &args[1];
println!("Using file {} as input.", filename);
let f = match File::open(filename) {
Ok(file) => file,
Err(e) => {
println!("Failed to open file {}. {:?}", filename, e);
process::exit(1);
}
};
let file = BufReader::new(&f);
let lines: Vec<String> = file.lines()
.map(|line| line.expect("Could not parse line."))
.collect();
let mut tracks = Tracks::new();
let mut carts = Carts::new();
let my = lines.len();
let mx = lines[0].len();
let mut id = 0;
for (y, line) in lines.iter().enumerate() {
let chars: Vec<char> = line.chars().collect();
for (x, &ch) in chars.iter().enumerate() {
if is_track(ch) {
tracks.insert((x, y), ch);
} else if is_cart(ch) {
let dir = cart_dir(ch);
let cart = Cart { dir, next_rot: -1, id };
carts.insert((x, y), cart);
id += 1;
}
}
}
// visualize(&tracks, &carts, my, mx);
let MAX_ITERS = 100000;
for iter in 0..MAX_ITERS {
let mut moved: HashSet<u32> = HashSet::new();
for y in 0..my {
for x in 0..mx {
if !cart_at(&carts, x, y) { continue; }
let mut cart = carts[&(x, y)].clone();
if moved.contains(&cart.id) { continue; }
let next_x = (x as i32 + cart.dir.0) as usize;
let next_y = (y as i32 + cart.dir.1) as usize;
if track_at(&tracks, next_x, next_y) {
let track = tracks[&(next_x, next_y)];
let new_dir = rot_cart(&cart, track);
if track == '+' {
cart.next_rot = (cart.next_rot + 2) % 3 - 1;
}
cart.dir = new_dir;
}
// Move cart
carts.remove(&(x, y));
moved.insert(cart.id);
if cart_at(&carts, next_x, next_y) {
println!("#{}: Collision at ({}, {})", iter, next_x, next_y);
carts.remove(&(next_x, next_y));
} else {
carts.insert((next_x, next_y), cart);
}
}
}
// visualize(&tracks, &carts, my, mx);
if carts.len() == 1 {
let keys = carts.keys();
for (last_x, last_y) in keys {
println!("#{}: Last position: ({}, {})", iter, last_x, last_y);
return;
}
}
else if carts.len() == 0 {
panic!("Even number of carts, no result!");
}
}
println!("Reached end of iterations");
}
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