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use aoc2024::direction::Direction::{self, *};
use aoc2024::matrix;
use core::cmp::max;
use std::collections::{BTreeSet, HashMap, HashSet};
use std::fmt;
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
enum Score {
Sc(u32, Direction),
Inf,
}
use Score::*;
impl fmt::Display for Score {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let repr = match self {
Self::Inf => "∞".to_string(),
Self::Sc(x, _dir) => x.to_string(),
};
write!(f, "{}", repr)
}
}
#[derive(Debug, Clone, Copy, PartialEq)]
enum Dot {
Start,
End,
Wall,
Empty,
}
use Dot::*;
impl fmt::Display for Dot {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let ch = match self {
Start => "S",
End => "E",
Wall => "#",
Empty => ".",
};
write!(f, "{}", ch)
}
}
impl Dot {
fn parse(c: char) -> Dot {
match c {
'S' => Start,
'E' => End,
'#' => Wall,
'.' => Empty,
_ => panic!("Invalid input"),
}
}
}
#[derive(Clone)]
struct M {
matrix: matrix::Matrix<Dot>,
unvisited: BTreeSet<(Score, matrix::Pos)>,
}
impl fmt::Display for M {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{}", self.matrix)
}
}
impl M {
fn new(text: &str) -> Self {
let matrix = matrix::Matrix::new(text, Dot::parse);
let mut unvisited = BTreeSet::new();
for i in 0..matrix.limit.0 {
for j in 0..matrix.limit.1 {
let dot = matrix.get((i, j));
let score = match dot {
Start => Some(Sc(0, Right)),
End => Some(Inf),
Wall => None,
Empty => Some(Inf),
};
if let Some(score) = score {
unvisited.insert((score, (i, j)));
};
}
}
M { matrix, unvisited }
}
fn adjacents(&self, pos: matrix::Pos, dir: Direction) -> Vec<(Direction, matrix::Pos)> {
dir.around()
.filter_map(|d| self.matrix.pos_move(pos, d.to_offset()).map(|p| (d, p)))
.collect()
}
fn print_with_dots(&self, positions: &HashSet<matrix::Pos>, dot: char) {
for i in 0..self.matrix.limit.0 {
for j in 0..self.matrix.limit.1 {
let p = (i, j);
if positions.contains(&p) {
print!("{}", dot);
} else {
print!("{}", self.matrix.get(p));
}
}
println!();
}
}
fn backtrack(
&self,
endpos: matrix::Pos,
mut prevs: HashMap<matrix::Pos, HashSet<matrix::Pos>>,
) -> u32 {
let mut visited: HashSet<matrix::Pos> = HashSet::new();
visited.insert(endpos);
let mut unvisited = vec![endpos];
while let Some(node) = unvisited.pop() {
if let Some(ps) = prevs.remove(&node) {
for p in ps {
if visited.insert(p) {
unvisited.push(p);
}
}
// println!("Adding {} because of {node:?}'s prevs:", ps.len());
// println!(" {:?}", ps);
// unvisited.append(&mut ps.into_iter().collect());
}
}
self.print_with_dots(&visited, 'O');
// println!("Visited: {visited:?}");
visited.len() as u32
}
fn dijkstra(&mut self) -> Option<(u32, u32)> {
let mut visited: HashSet<matrix::Pos> = HashSet::new();
let mut prevs: HashMap<matrix::Pos, HashSet<matrix::Pos>> = HashMap::new();
let mut result = (0, (0, 0));
while let Some((score, pos)) = self.unvisited.pop_first() {
self.print_with_dots(&visited, 'O');
self.print_with_dots(
&self
.unvisited
.iter()
.filter_map(|(sc, p)| if let Sc(_, _) = sc { Some(*p) } else { None })
.collect(),
'?',
);
let Sc(scoreint, dir) = score else {
break;
};
let dot = self.matrix.get(pos);
if dot == &End {
// self.print_with_dots(&visited, 'O');
result = (scoreint, pos);
};
// println!("Visiting ({pos:?}) with score = {score:?}");
let adjs: Vec<(Score, matrix::Pos)> = self
.adjacents(pos, dir)
.into_iter()
.map(|(d, p)| (d, p, self.matrix.get(p)))
.filter(|&(_d, _p, dot)| dot != &Wall)
.map(|(d, p, _dot)| (set_dot_score(scoreint, &score, dir, d), p))
.collect();
// println!("Adjacents when facing {:?}: {adjs:?}", dir);
for adj in adjs {
if visited.insert(adj.1) {
self.unvisited.insert((adj.0, adj.1));
}
prevs.entry(adj.1).or_default().insert(pos);
}
// println!("{}", self);
}
// }
// unvisited.push((0, self.start));
Some((result.0, self.backtrack(result.1, prevs)))
}
}
fn set_dot_score(currscore: u32, dotscore: &Score, dir: Direction, newdir: Direction) -> Score {
let new_score = Sc(if dir == newdir { 1 } else { 1001 } + currscore, newdir);
max(*dotscore, new_score)
}
fn p1(input: &str) -> String {
let mut m = M::new(input);
println!("{m}");
let result = m.dijkstra().unwrap();
result.0.to_string()
}
fn p2(input: &str) -> String {
let mut m = M::new(input);
println!("{m}");
let result = m.dijkstra().unwrap();
result.1.to_string()
}
fn main() {
aoc2024::run_day("16", p1, p2);
}
|
