bendns' repos / aoc
heh
Diffstat (limited to 'src/main.rs')
-rw-r--r--src/main.rs247
1 files changed, 229 insertions, 18 deletions
diff --git a/src/main.rs b/src/main.rs
index d878a4e..586ad1b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,7 @@
#![allow(confusable_idents, uncommon_codepoints, mixed_script_confusables)]
#![feature(
array_windows,
+ slice_take,
test,
slice_as_chunks,
array_chunks,
@@ -9,30 +10,240 @@
)]
extern crate test;
mod util;
-
pub use util::prelude::*;
-/// generated by passing 1, 0{20} and 0, 1, 0{19}, etc to the original
-const INTERPOLATION_P1: [i32; 21] = [
- 1, -21, 210, -1330, 5985, -20349, 54264, -116280, 203490, -293930, 352716, -352716, 293930,
- -203490, 116280, -54264, 20349, -5985, 1330, -210, 21,
-];
-/// just the reversed version of [`INTERPOLATION_P1`]
-const INTERPOLATION_P2: [i32; 21] = [
- 21, -210, 1330, -5985, 20349, -54264, 116280, -203490, 293930, -352716, 352716, -293930,
- 203490, -116280, 54264, -20349, 5985, -1330, 210, -21, 1,
-];
+#[repr(u8)]
+#[derive(Copy, Clone, PartialEq, Eq)]
+enum Pipe {
+ /// │
+ NS = b'|',
+ /// ─
+ EW = b'-',
+ /// ╰
+ NE = b'L',
+ /// ╯
+ NW = b'J',
+ /// ╮
+ SW = b'7',
+ /// ╭
+ SE = b'F',
+ #[allow(dead_code)] // transmute() go brr
+ Ground = b'.',
+ Start = b'S',
+}
+
+#[derive(Copy, Clone, Debug)]
+enum D {
+ N,
+ E,
+ S,
+ W,
+}
+
+impl Pipe {
+ fn ch(self) -> char {
+ match self {
+ Pipe::NS => '│',
+ Pipe::EW => '─',
+ Pipe::NE => '╰',
+ Pipe::NW => '╯',
+ Pipe::SW => '╮',
+ Pipe::SE => '╭',
+ Pipe::Ground => '.',
+ Pipe::Start => 'S',
+ }
+ }
+
+ fn n(self) -> bool {
+ matches!(self, Pipe::NS | Pipe::NE | Pipe::NW)
+ }
+
+ fn e(self) -> bool {
+ matches!(self, Pipe::EW | Pipe::NE | Pipe::SE)
+ }
+
+ fn s(self) -> bool {
+ matches!(self, Pipe::SW | Pipe::NS | Pipe::SE)
+ }
+
+ fn w(self) -> bool {
+ matches!(self, Pipe::EW | Pipe::NW | Pipe::SW)
+ }
+}
+
+impl std::fmt::Display for Pipe {
+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+ write!(f, "{}", self.ch())
+ }
+}
+
+struct Map<const S: usize> {
+ map: [[Pipe; S]; S],
+}
+
+impl<const N: usize> std::fmt::Display for Map<N> {
+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+ for x in self.map {
+ for y in x {
+ write!(f, "{y}")?;
+ }
+ writeln!(f)?;
+ }
+ Ok(())
+ }
+}
+
+impl<const S: usize> Map<S> {
+ fn at(&self, x: u8, y: u8) -> Pipe {
+ self.map[y.nat()][x.nat()]
+ }
+
+ fn start(&self, x: u8, y: u8) -> (Pipe, D) {
+ let surround = [
+ self.at(x - 1, y).s() as u8,
+ self.at(x, y + 1).w() as u8,
+ self.at(x, y - 1).e() as u8,
+ self.at(x + 1, y).n() as u8,
+ ];
+ match surround {
+ [1, 1, 0, 0] => (Pipe::NE, D::E),
+ [1, 0, 1, 0] => (Pipe::NS, D::S),
+ [1, 0, 0, 1] => (Pipe::NW, D::W),
+ [0, 1, 1, 0] => (Pipe::SE, D::S),
+ [0, 1, 0, 1] => (Pipe::EW, D::W),
+ [0, 0, 1, 1] => (Pipe::SW, D::S),
+ _ => dang!(),
+ }
+ }
+
+ fn go(&self, p: Pipe, x: &mut u8, y: &mut u8, d: D) {
+ use D::*;
+ #[rustfmt::skip]
+ macro_rules! n { () => { *y -= 1 }; }
+ #[rustfmt::skip]
+ macro_rules! e { () => { *x += 1 }; }
+ #[rustfmt::skip]
+ macro_rules! s { () => { *y += 1 }; }
+ #[rustfmt::skip]
+ macro_rules! w { () => { *x -= 1 }; }
+ mat!(p {
+ Pipe::NS => mat!(d {
+ N => n!(),
+ S => s!(),
+ }),
+ Pipe::EW => mat!(d {
+ E => e!(),
+ W => w!(),
+ }),
+ Pipe::NE => mat!(d {
+ N => n!(),
+ E => e!(),
+ }),
+ Pipe::NW => mat!(d {
+ N => n!(),
+ W => w!(),
+ }),
+ Pipe::SW => mat!(d {
+ S => s!(),
+ W => w!(),
+ }),
+ Pipe::SE => mat!(d {
+ E => e!(),
+ S => s!(),
+ }),
+ })
+ }
+
+ fn turn(&self, p: Pipe, d: &mut D) {
+ use D::*;
+ #[rustfmt::skip]
+ macro_rules! n { () => { *d = N }; }
+ #[rustfmt::skip]
+ macro_rules! e { () => { *d = E }; }
+ #[rustfmt::skip]
+ macro_rules! s { () => { *d = S }; }
+ #[rustfmt::skip]
+ macro_rules! w { () => { *d = W }; }
+ mat!(p {
+ Pipe::NS => mat!(d {
+ N => n!(), // keep going north
+ S => s!(), // keep going south
+ }),
+ Pipe::EW => mat!(d {
+ E => e!(), // keep going east
+ W => w!(), // keep going west
+ }),
+ Pipe::NE => mat!(d {
+ W => n!(), // start going north
+ S => e!(), // start going east
+ }),
+ Pipe::NW => mat!(d {
+ E => n!(), // start going north
+ S => w!(), // start going west
+ }),
+ Pipe::SW => mat!(d {
+ E => s!(), // start going south
+ N => w!(), // start going west
+ }),
+ Pipe::SE => mat!(d {
+ N => e!(), // start going east
+ W => s!(), // start going south
+ }),
+ })
+ }
+
+ fn run(&self) -> usize {
+ let mut x = 0;
+ let mut y = 0;
+ for (r, j) in self.map.iter().zip(0..) {
+ for (&c, i) in r.iter().zip(0..) {
+ if c == Pipe::Start {
+ x = i;
+ y = j;
+ break;
+ }
+ }
+ }
+
+ let (mut at, mut dir) = self.start(x, y);
+ let mut steps = 1;
+ loop {
+ self.go(at, &mut x, &mut y, dir);
+ at = self.at(x, y);
+ if at == Pipe::Start {
+ break;
+ }
+ self.turn(at, &mut dir);
+ steps += 1;
+ }
+ steps / 2
+ }
+}
-pub fn solve(a: impl Iterator<Item = i32>, interp: [i32; 21]) -> i32 {
- a.zip(interp.into_iter())
- .map(|(a, b)| a as i64 * b as i64)
- .sum::<i64>() as i32
+impl<const S: usize> From<&[u8]> for Map<S> {
+ fn from(mut i: &[u8]) -> Self {
+ Self {
+ map: (0..S)
+ .map(|n| {
+ let inner = i
+ .take(..S)
+ .α()
+ .iter()
+ .map(|&b| unsafe { std::mem::transmute(b) })
+ .Ν();
+ if n != S - 1 {
+ i.skip(1);
+ }
+ inner
+ })
+ .Ν(),
+ }
+ }
}
pub fn run(i: &str) -> impl Display {
- i.行()
- .map(|x| solve(&mut x.κ(), INTERPOLATION_P2))
- .sum::<i32>()
+ let map = Map::<140>::from(i.as_bytes());
+ map.run()
}
fn main() {