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|
use rpds::RedBlackTreeSet;
use std::io;
use std::io::prelude::*;
use std::iter;
use std::iter::FromIterator;
use std::process;
use structopt::StructOpt;
#[derive(Debug, StructOpt)]
#[structopt(name = "Day 24: Planet of Discord")]
/// Simulates the life and death of Eris bugs
///
/// See https://adventofcode.com/2019/day/24 for details.
struct Opt {
/// How many iterations of the game of life should be run
/// If not provided, runs until a state appears twice.
#[structopt(short = "n")]
depth: Option<usize>,
/// Interprets the map as being one part of an infinite fractal map
#[structopt(short = "f")]
fractal: bool,
}
fn main() {
let stdin = io::stdin();
let opt = Opt::from_args();
let initial_state: State = stdin
.lock()
.lines()
.map(|x| exit_on_failed_assertion(x, "Error reading input"))
.collect::<State>()
.with_fractal_mode(opt.fractal);
let final_state = match opt.depth {
Some(depth) => initial_state.n_steps_forward(depth),
None => initial_state.first_repeated_state(),
};
println!("Bugs: {}", final_state.alive.size());
println!("Biodiversity: {}", final_state.biodiversity_rating());
}
fn exit_on_failed_assertion<A, E: std::error::Error>(data: Result<A, E>, message: &str) -> A {
match data {
Ok(data) => data,
Err(e) => {
eprintln!("{}: {}", message, e);
process::exit(1);
}
}
}
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
struct State {
alive: RedBlackTreeSet<Coordinate>,
fractal_mode: bool,
}
impl FromIterator<String> for State {
fn from_iter<T: IntoIterator<Item = String>>(iter: T) -> Self {
State {
alive: iter
.into_iter()
.enumerate()
.flat_map(move |(y, line)| {
line.chars()
.enumerate()
.filter(move |(_x, c)| *c == '#')
.map(move |(x, _c)| Coordinate {
x: x as isize,
y: y as isize,
depth: 0,
})
.collect::<Vec<Coordinate>>()
})
.collect(),
fractal_mode: false,
}
}
}
impl State {
fn with_fractal_mode(&self, fractal_mode: bool) -> State {
State {
fractal_mode,
..self.clone()
}
}
fn n_steps_forward(&self, n: usize) -> Self {
iter::successors(Some(self.clone()), |state| Some(state.next()))
.nth(n)
.unwrap()
}
fn first_repeated_state(&self) -> State {
iter::successors(
Some((RedBlackTreeSet::new(), self.clone())),
|(seen, state)| Some((seen.insert(state.clone()), state.next())),
)
.find(|(seen, state)| seen.contains(state))
.unwrap()
.1
}
fn next(&self) -> State {
State {
alive: self
.still_alive_next_round()
.chain(self.comes_alive_next_round())
.collect(),
..self.clone()
}
}
fn biodiversity_rating(&self) -> usize {
self.alive
.iter()
.map(|coord| 2_usize.pow((coord.y * 5 + coord.x) as u32))
.sum()
}
fn still_alive_next_round<'a>(&'a self) -> impl Iterator<Item = Coordinate> + 'a {
self.alive
.iter()
.filter(move |coord| self.count_alive_neighbours(**coord) == 1)
.cloned()
}
fn comes_alive_next_round<'a>(&'a self) -> impl Iterator<Item = Coordinate> + 'a {
self.alive
.iter()
.flat_map(move |coord| self.neighbours(*coord))
.filter(move |coord| !self.alive.contains(coord))
.filter(move |coord| {
self.count_alive_neighbours(*coord) == 1 || self.count_alive_neighbours(*coord) == 2
})
}
fn count_alive_neighbours(&self, coordinate: Coordinate) -> usize {
self.neighbours(coordinate)
.into_iter()
.filter(|coord| self.alive.contains(coord))
.count()
}
fn neighbours(&self, coordinate: Coordinate) -> Vec<Coordinate> {
if self.fractal_mode {
[(-1, 0), (1, 0), (0, -1), (0, 1)]
.into_iter()
.map(|(dx, dy)| Coordinate {
x: coordinate.x + dx,
y: coordinate.y + dy,
depth: coordinate.depth,
})
.flat_map(move |coord| match (coord.x, coord.y) {
(x, _y) if x < 0 => vec![Coordinate {
x: 1,
y: 2,
depth: coord.depth - 1,
}]
.into_iter(),
(_x, y) if y < 0 => vec![Coordinate {
x: 2,
y: 1,
depth: coord.depth - 1,
}]
.into_iter(),
(x, _y) if x >= 5 => vec![Coordinate {
x: 3,
y: 2,
depth: coord.depth - 1,
}]
.into_iter(),
(_x, y) if y >= 5 => vec![Coordinate {
x: 2,
y: 3,
depth: coord.depth - 1,
}]
.into_iter(),
(2, 2) => match (coordinate.x, coordinate.y) {
(1, 2) => (0..5)
.map(|y| Coordinate {
x: 0,
y,
depth: coord.depth + 1,
})
.collect::<Vec<_>>()
.into_iter(),
(2, 1) => (0..5)
.map(|x| Coordinate {
x,
y: 0,
depth: coord.depth + 1,
})
.collect::<Vec<_>>()
.into_iter(),
(3, 2) => (0..5)
.map(|y| Coordinate {
x: 4,
y,
depth: coord.depth + 1,
})
.collect::<Vec<_>>()
.into_iter(),
(2, 3) => (0..5)
.map(|x| Coordinate {
x,
y: 4,
depth: coord.depth + 1,
})
.collect::<Vec<_>>()
.into_iter(),
(_, _) => vec![].into_iter(),
},
_ => vec![coord.clone()].into_iter(),
})
.collect()
} else {
[(-1, 0), (1, 0), (0, -1), (0, 1)]
.into_iter()
.map(|(dx, dy)| Coordinate {
x: coordinate.x + dx,
y: coordinate.y + dy,
depth: coordinate.depth,
})
.filter(|coord| coord.x >= 0 && coord.x < 5 && coord.y >= 0 && coord.y < 5)
.collect()
}
}
}
#[derive(Debug, Clone, Copy, PartialOrd, Ord, PartialEq, Eq)]
struct Coordinate {
x: isize,
y: isize,
depth: isize,
}
|
