Solve day13

1 files changed, 218 insertions, 0 deletions

diff --git a/day13/src/main.rs b/day13/src/main.rs
new file mode 100644
index 0000000..d53423b
--- /dev/null
+++ b/day13/src/main.rs
@@ -0,0 +1,218 @@
+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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