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|
use std::io;
use std::io::BufRead;
use std::collections::HashMap;
#[derive(Clone, PartialEq, Eq, Hash)]
struct Pos { x: usize, y: usize }
#[derive(Clone)]
struct Dir { x: i32, y: i32 }
impl Dir {
fn rotright(&self) -> Dir {
Dir { x: -self.y, y: self.x }
}
fn rotleft(&self) -> Dir {
Dir { x: self.y, y: -self.x }
}
}
enum Choice {
Left,
Forward,
Right,
}
impl Choice {
fn incr(&mut self) {
match self {
Choice::Left => *self = Choice::Forward,
Choice::Forward => *self = Choice::Right,
Choice::Right => *self = Choice::Left,
}
}
fn apply(&self, dir: &Dir) -> Dir {
match self {
Choice::Left => dir.rotleft(),
Choice::Forward => dir.clone(),
Choice::Right => dir.rotright(),
}
}
}
struct Cart {
pos: Pos,
dir: Dir,
choice: Choice,
}
impl Cart {
fn nextpos(&self) -> Pos {
Pos { x: (self.pos.x as i32 + self.dir.x) as usize,
y: (self.pos.y as i32 + self.dir.y) as usize }
}
}
fn newdir(dir: &Dir, c: u8) -> Dir {
// println!(" newdir {},{} {}", dir.x, dir.y, std::char::from_u32(c as u32).unwrap());
if c == '|' as u8 || c == '-' as u8 {
Dir { x: dir.x, y: dir.y }
} else if c == '/' as u8 {
if dir.y == 0 {
dir.rotleft()
} else {
dir.rotright()
}
} else if c == '\\' as u8 {
if dir.y == 0 {
dir.rotright()
} else {
dir.rotleft()
}
} else {
println!("<{}>", c);
unreachable!();
}
}
#[allow(dead_code)]
fn print_dir(dir: &Dir) -> char {
match dir {
Dir{x:1,y:0} => '>',
Dir{x:-1,y:0} => '<',
Dir{x:0,y:1} => 'v',
Dir{x:0,y:-1} => '^',
Dir{..} => '?',
}
}
#[allow(dead_code)]
fn print_grid(grid: &Vec<Vec<u8>>, carts: &Vec<Cart>) {
let mut hascart: HashMap<Pos, usize> = HashMap::new();
for (i, cart) in carts.iter().enumerate() {
hascart.insert(cart.pos.clone(), i);
}
for y in 0..grid.len() {
for x in 0..grid[y].len() {
match hascart.get(&Pos { x, y }) {
Some(&idx) => {
print!("{}", print_dir(&carts[idx].dir));
}
None => {
print!("{}", std::char::from_u32(grid[y][x] as u32).unwrap());
}
}
}
println!("");
}
}
pub fn main<T: BufRead>(reader: T) -> io::Result<(String, String)> {
let mut grid: Vec<Vec<u8>> = reader.lines().map(|l| l.unwrap().as_bytes().to_vec()).collect();
let h = grid.len();
let w = grid[0].len();
let mut hascart = Vec::new();
for _ in 0..h {
hascart.push(vec![false; w]);
}
let mut carts: Vec<Cart> = Vec::new();
for y in 0..h {
for x in 0..w {
macro_rules! grid_process {
( $c1:expr, $c2:expr, $dx:expr, $dy:expr ) => {
if grid[y][x] == $c1 as u8 {
grid[y][x] = $c2 as u8;
carts.push(Cart { pos: Pos { x, y }, dir: Dir { x: $dx, y: $dy }, choice: Choice::Left });
hascart[y][x] = true;
}
}
}
grid_process!('>', '-', 1, 0);
grid_process!('<', '-', -1, 0);
grid_process!('^', '|', 0, -1);
grid_process!('v', '|', 0, 1);
}
}
let mut first_crash = None;
let part2;
loop {
let mut to_remove = Vec::new();
for (i, mut cart) in carts.iter_mut().enumerate() {
if !hascart[cart.pos.y][cart.pos.x] {
to_remove.push(i);
continue;
}
let pos2 = cart.nextpos();
let c = grid[pos2.y][pos2.x];
// println!("cart at {},{} {},{}", cart.pos.x, cart.pos.y, cart.dir.x, cart.dir.y);
let dir2;
if c == '+' as u8 {
dir2 = cart.choice.apply(&cart.dir);
cart.choice.incr();
} else {
dir2 = newdir(&cart.dir, c);
}
hascart[cart.pos.y][cart.pos.x] = false;
if hascart[pos2.y][pos2.x] {
if first_crash.is_none() {
first_crash = Some(pos2.clone());
}
to_remove.push(i);
hascart[pos2.y][pos2.x] = false;
} else {
hascart[pos2.y][pos2.x] = true;
cart.pos = pos2;
cart.dir = dir2;
}
}
for idx in to_remove {
carts.swap_remove(idx);
}
if carts.len() == 1 {
part2 = format!("{},{}", carts[0].pos.x, carts[0].pos.y);
break;
}
carts.sort_by_key(|cart| (cart.pos.y, cart.pos.x));
// print_grid(&grid, &carts);
}
let part1 = match first_crash {
Some(pos) => format!("{},{}", pos.x, pos.y),
None => unreachable!()
};
Ok((part1, part2))
}
|
