339 lines
11 KiB
Rust
339 lines
11 KiB
Rust
|
extern crate regex;
|
||
|
|
|
||
|
|
use std::collections::{HashMap, HashSet};
|
||
|
|
use std::error::Error;
|
||
|
|
use std::fs;
|
||
|
|
use std::result;
|
||
|
|
use std::str::FromStr;
|
||
|
|
|
||
|
|
type Result<T> = result::Result<T, Box<Error>>;
|
||
|
|
|
||
|
|
const INPUT: &str = "inputs/13.txt";
|
||
|
|
|
||
|
|
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy)]
|
||
|
|
pub struct Vector {
|
||
|
|
pub y: usize,
|
||
|
|
pub x: usize,
|
||
|
|
}
|
||
|
|
|
||
|
|
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
|
||
|
|
enum Turn {
|
||
|
|
Left,
|
||
|
|
Straight,
|
||
|
|
Right,
|
||
|
|
Reverse,
|
||
|
|
}
|
||
|
|
|
||
|
|
const INTER_SEQ: [Turn; 3] = [Turn::Left, Turn::Straight, Turn::Right];
|
||
|
|
|
||
|
|
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
|
||
|
|
enum Direction {
|
||
|
|
North,
|
||
|
|
South,
|
||
|
|
East,
|
||
|
|
West,
|
||
|
|
}
|
||
|
|
|
||
|
|
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
|
||
|
|
struct Cart {
|
||
|
|
position: Vector,
|
||
|
|
direction: Direction,
|
||
|
|
next_turn: u8,
|
||
|
|
}
|
||
|
|
|
||
|
|
#[derive(Debug, PartialEq)]
|
||
|
|
struct Track {
|
||
|
|
carts: Vec<Cart>,
|
||
|
|
turns: HashMap<Vector, (Direction, Direction)>,
|
||
|
|
intersections: HashSet<Vector>,
|
||
|
|
}
|
||
|
|
|
||
|
|
impl FromStr for Track {
|
||
|
|
type Err = Box<Error>;
|
||
|
|
|
||
|
|
fn from_str(s: &str) -> Result<Track> {
|
||
|
|
let mut carts = vec![];
|
||
|
|
let mut turns = HashMap::new();
|
||
|
|
let mut intersections = HashSet::new();
|
||
|
|
let mut incomplete_circuits: HashMap<(usize, usize), usize> = HashMap::new();
|
||
|
|
|
||
|
|
for (row_index, row) in s.lines().enumerate() {
|
||
|
|
let mut top_start: Option<usize> = None;
|
||
|
|
let mut bottom_start: Option<usize> = None;
|
||
|
|
for c in row.char_indices() {
|
||
|
|
match c {
|
||
|
|
(col_index, '\\') => match top_start {
|
||
|
|
Some(start) => {
|
||
|
|
incomplete_circuits.insert((start, col_index), row_index);
|
||
|
|
turns.insert(
|
||
|
|
Vector {
|
||
|
|
x: col_index,
|
||
|
|
y: row_index,
|
||
|
|
},
|
||
|
|
(Direction::South, Direction::West),
|
||
|
|
);
|
||
|
|
top_start = None;
|
||
|
|
}
|
||
|
|
None => {
|
||
|
|
bottom_start = Some(col_index);
|
||
|
|
turns.insert(
|
||
|
|
Vector {
|
||
|
|
x: col_index,
|
||
|
|
y: row_index,
|
||
|
|
},
|
||
|
|
(Direction::North, Direction::East),
|
||
|
|
);
|
||
|
|
}
|
||
|
|
},
|
||
|
|
(col_index, '/') => match bottom_start {
|
||
|
|
Some(start) => match incomplete_circuits.remove(&(start, col_index)) {
|
||
|
|
Some(top_row) => {
|
||
|
|
turns.insert(
|
||
|
|
Vector {
|
||
|
|
x: col_index,
|
||
|
|
y: row_index,
|
||
|
|
},
|
||
|
|
(Direction::West, Direction::North),
|
||
|
|
);
|
||
|
|
bottom_start = None;
|
||
|
|
}
|
||
|
|
None => {
|
||
|
|
return Err(From::from(
|
||
|
|
"Malformed track, circuit bottom without top",
|
||
|
|
))
|
||
|
|
}
|
||
|
|
},
|
||
|
|
None => {
|
||
|
|
top_start = Some(col_index);
|
||
|
|
turns.insert(
|
||
|
|
Vector {
|
||
|
|
x: col_index,
|
||
|
|
y: row_index,
|
||
|
|
},
|
||
|
|
(Direction::East, Direction::South),
|
||
|
|
);
|
||
|
|
}
|
||
|
|
},
|
||
|
|
(col_index, '+') => {
|
||
|
|
intersections.insert(Vector {
|
||
|
|
x: col_index,
|
||
|
|
y: row_index,
|
||
|
|
});
|
||
|
|
}
|
||
|
|
(col_index, '^') => carts.push(Cart {
|
||
|
|
position: Vector {
|
||
|
|
x: col_index,
|
||
|
|
y: row_index,
|
||
|
|
},
|
||
|
|
direction: Direction::North,
|
||
|
|
next_turn: 0,
|
||
|
|
}),
|
||
|
|
(col_index, 'v') => carts.push(Cart {
|
||
|
|
position: Vector {
|
||
|
|
x: col_index,
|
||
|
|
y: row_index,
|
||
|
|
},
|
||
|
|
direction: Direction::South,
|
||
|
|
next_turn: 0,
|
||
|
|
}),
|
||
|
|
(col_index, '>') => carts.push(Cart {
|
||
|
|
position: Vector {
|
||
|
|
x: col_index,
|
||
|
|
y: row_index,
|
||
|
|
},
|
||
|
|
direction: Direction::East,
|
||
|
|
next_turn: 0,
|
||
|
|
}),
|
||
|
|
(col_index, '<') => carts.push(Cart {
|
||
|
|
position: Vector {
|
||
|
|
x: col_index,
|
||
|
|
y: row_index,
|
||
|
|
},
|
||
|
|
direction: Direction::West,
|
||
|
|
next_turn: 0,
|
||
|
|
}),
|
||
|
|
_ => {}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
Ok(Track {
|
||
|
|
carts,
|
||
|
|
turns,
|
||
|
|
intersections,
|
||
|
|
})
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl Direction {
|
||
|
|
fn turn(self, turn: Turn) -> Direction {
|
||
|
|
match turn {
|
||
|
|
Turn::Left => match self {
|
||
|
|
Direction::North => Direction::West,
|
||
|
|
Direction::South => Direction::East,
|
||
|
|
Direction::East => Direction::North,
|
||
|
|
Direction::West => Direction::South,
|
||
|
|
},
|
||
|
|
Turn::Right => match self {
|
||
|
|
Direction::North => Direction::East,
|
||
|
|
Direction::South => Direction::West,
|
||
|
|
Direction::East => Direction::South,
|
||
|
|
Direction::West => Direction::North,
|
||
|
|
},
|
||
|
|
Turn::Reverse => match self {
|
||
|
|
Direction::North => Direction::South,
|
||
|
|
Direction::South => Direction::North,
|
||
|
|
Direction::East => Direction::West,
|
||
|
|
Direction::West => Direction::East,
|
||
|
|
},
|
||
|
|
Turn::Straight => self,
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl Cart {
|
||
|
|
fn turn(&mut self, turn: Turn) {
|
||
|
|
self.direction = self.direction.turn(turn);
|
||
|
|
}
|
||
|
|
|
||
|
|
fn follow_turn(&mut self, turn_arms: (Direction, Direction)) {
|
||
|
|
let entering_from = self.direction.turn(Turn::Reverse);
|
||
|
|
|
||
|
|
if entering_from == turn_arms.0 {
|
||
|
|
self.direction = turn_arms.1;
|
||
|
|
} else if entering_from == turn_arms.1 {
|
||
|
|
self.direction = turn_arms.0;
|
||
|
|
} else {
|
||
|
|
panic!("Cart entered turn from an invalid direction");
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl Track {
|
||
|
|
fn run_tick(&mut self) -> Option<Vector> {
|
||
|
|
let mut cart_positions: HashSet<Vector> = HashSet::new();
|
||
|
|
for cart in self.carts.iter() {
|
||
|
|
cart_positions.insert(cart.position);
|
||
|
|
}
|
||
|
|
|
||
|
|
for cart in self.carts.iter_mut() {
|
||
|
|
let Vector { x, y } = cart.position;
|
||
|
|
cart_positions.remove(&cart.position);
|
||
|
|
cart.position = match cart.direction {
|
||
|
|
Direction::North => Vector { x, y: y - 1 },
|
||
|
|
Direction::South => Vector { x, y: y + 1 },
|
||
|
|
Direction::East => Vector { x: x + 1, y },
|
||
|
|
Direction::West => Vector { x: x - 1, y },
|
||
|
|
};
|
||
|
|
|
||
|
|
if let Some(turn_arms) = self.turns.get(&cart.position) {
|
||
|
|
cart.follow_turn(*turn_arms);
|
||
|
|
}
|
||
|
|
|
||
|
|
if self.intersections.contains(&cart.position) {
|
||
|
|
cart.turn(INTER_SEQ[cart.next_turn as usize]);
|
||
|
|
cart.next_turn = (cart.next_turn + 1) % INTER_SEQ.len() as u8;
|
||
|
|
}
|
||
|
|
|
||
|
|
if cart_positions.contains(&cart.position) {
|
||
|
|
return Some(cart.position);
|
||
|
|
}
|
||
|
|
|
||
|
|
cart_positions.insert(cart.position);
|
||
|
|
}
|
||
|
|
self.carts.sort_unstable();
|
||
|
|
None
|
||
|
|
}
|
||
|
|
|
||
|
|
fn find_first_collision(&mut self) -> Vector {
|
||
|
|
let mut collision: Option<Vector> = None;
|
||
|
|
while collision.is_none() {
|
||
|
|
collision = self.run_tick();
|
||
|
|
}
|
||
|
|
collision.unwrap()
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
fn read_track(filename: &str) -> Result<Track> {
|
||
|
|
let input = fs::read_to_string(filename)?;
|
||
|
|
Ok(input.parse()?)
|
||
|
|
}
|
||
|
|
|
||
|
|
pub fn solve_part1() -> Result<Vector> {
|
||
|
|
let mut track = read_track(INPUT)?;
|
||
|
|
Ok(track.find_first_collision())
|
||
|
|
}
|
||
|
|
|
||
|
|
#[cfg(test)]
|
||
|
|
mod tests {
|
||
|
|
use super::*;
|
||
|
|
|
||
|
|
const TEST_INPUT: &str = "inputs/13_test.txt";
|
||
|
|
fn test_track() -> Track {
|
||
|
|
Track {
|
||
|
|
carts: vec![
|
||
|
|
Cart {
|
||
|
|
position: Vector { x: 2, y: 0 },
|
||
|
|
direction: Direction::East,
|
||
|
|
next_turn: 0,
|
||
|
|
},
|
||
|
|
Cart {
|
||
|
|
position: Vector { x: 9, y: 3 },
|
||
|
|
direction: Direction::South,
|
||
|
|
next_turn: 0,
|
||
|
|
},
|
||
|
|
],
|
||
|
|
turns: vec![
|
||
|
|
(Vector { x: 0, y: 0 }, (Direction::East, Direction::South)),
|
||
|
|
(Vector { x: 4, y: 0 }, (Direction::South, Direction::West)),
|
||
|
|
(Vector { x: 4, y: 4 }, (Direction::West, Direction::North)),
|
||
|
|
(Vector { x: 0, y: 4 }, (Direction::North, Direction::East)),
|
||
|
|
(Vector { x: 7, y: 1 }, (Direction::East, Direction::South)),
|
||
|
|
(Vector { x: 12, y: 1 }, (Direction::South, Direction::West)),
|
||
|
|
(Vector { x: 12, y: 4 }, (Direction::West, Direction::North)),
|
||
|
|
(Vector { x: 7, y: 4 }, (Direction::North, Direction::East)),
|
||
|
|
(Vector { x: 2, y: 2 }, (Direction::East, Direction::South)),
|
||
|
|
(Vector { x: 9, y: 2 }, (Direction::South, Direction::West)),
|
||
|
|
(Vector { x: 9, y: 5 }, (Direction::West, Direction::North)),
|
||
|
|
(Vector { x: 2, y: 5 }, (Direction::North, Direction::East)),
|
||
|
|
]
|
||
|
|
.iter()
|
||
|
|
.cloned()
|
||
|
|
.collect(),
|
||
|
|
intersections: vec![
|
||
|
|
Vector { x: 4, y: 2 },
|
||
|
|
Vector { x: 7, y: 2 },
|
||
|
|
Vector { x: 2, y: 4 },
|
||
|
|
Vector { x: 9, y: 4 },
|
||
|
|
]
|
||
|
|
.iter()
|
||
|
|
.cloned()
|
||
|
|
.collect(),
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn reads_track_file() {
|
||
|
|
let track = read_track(TEST_INPUT).unwrap();
|
||
|
|
assert_eq!(track, test_track());
|
||
|
|
}
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn runs_one_tick() {
|
||
|
|
let mut track_after = test_track();
|
||
|
|
track_after.carts[0].position.x = 3;
|
||
|
|
track_after.carts[1].position.y = 4;
|
||
|
|
track_after.carts[1].direction = Direction::East;
|
||
|
|
track_after.carts[1].next_turn = 1;
|
||
|
|
let mut track = test_track();
|
||
|
|
track.run_tick();
|
||
|
|
assert_eq!(track, track_after);
|
||
|
|
}
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn finds_first_collision() {
|
||
|
|
let mut track = test_track();
|
||
|
|
assert_eq!(track.find_first_collision(), Vector { x: 7, y: 3 });
|
||
|
|
}
|
||
|
|
}
|