bendns' repos / aoc
heh
Diffstat (limited to 'src/main.rs')
-rw-r--r--src/main.rs51
1 files changed, 32 insertions, 19 deletions
diff --git a/src/main.rs b/src/main.rs
index 2a4fda5..d755ae1 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,24 +2,41 @@
#![feature(array_windows, test, slice_as_chunks, array_chunks)]
extern crate test;
mod util;
-pub use explicit_cast::prelude::*;
pub use util::prelude::*;
-fn solve(i: &str) -> impl Display {
+#[inline(always)]
+fn k(s: &str) -> u16 {
+ unsafe { *s.as_ptr().cast::<[u8; 3]>() }
+ .iter()
+ .enumerate()
+ .map(|(i, &b)| ((b - b'A') as u16) << (i * 5))
+ .sum()
+}
+
+fn start(x: u16) -> bool {
+ (x >> (2 * 5) & 0b11111) == 0u16
+}
+
+fn end(x: u16) -> bool {
+ (x >> (2 * 5) & 0b11111) == (b'Z' - b'A') as u16
+}
+
+pub fn run(i: &str) -> impl Display {
let mut lines = i.lines();
let line = lines.by_ref().Δ().as_bytes();
let map = lines
.skip(1)
.map(|x| {
x.μ('=')
- .mr(|x| x.trim()[1..x.len() - 2].μ(',').ml(str::trim).mr(str::trim))
+ .mr(|x| x.trim()[1..x.len() - 2].μ(',').mb(str::trim).mb(k))
.ml(str::trim)
+ .ml(k)
})
.collect::<HashMap<_, _>>();
let mut positions = map
.keys()
.map(|&x| x)
- .filter(|x| x.ends_with('A'))
+ .filter(|&x| start(x))
.collect::<Box<[_]>>();
let mut steps = 1u64;
let mut findings = HashMap::new();
@@ -29,41 +46,37 @@ fn solve(i: &str) -> impl Display {
break;
}
for p in &mut *positions {
- let at = map[*p];
+ let at = map[p];
*p = match instruction {
b'L' => at.0,
b'R' => at.1,
_ => dang!(),
};
- if p.ends_with('Z') {
- if let Some(&c) = findings.get(*p) {
- if !cycle.contains_key(*p) {
- println!("cycle {} ({steps})", steps - c);
- cycle.insert(*p, steps - c);
+ if end(*p) {
+ if let Some(&c) = findings.get(p) {
+ match cycle.entry(*p) {
+ Entry::Occupied(_) => {}
+ Entry::Vacant(x) => {
+ x.insert(steps - c);
+ }
}
} else {
- println!("register {p} ({steps})");
findings.insert(*p, steps);
}
}
}
steps += 1;
}
- print!("lcm(");
- for cycle in cycle.values() {
- print!("{cycle},")
- }
- println!(")");
- 0
+ lcm(cycle.values().copied())
}
fn main() {
let i = include_str!("inp.txt").trim();
- println!("{}", solve(i));
+ println!("{}", run(i));
}
#[bench]
fn bench(b: &mut test::Bencher) {
let i = boxd(include_str!("inp.txt").trim());
- b.iter(|| solve(i));
+ b.iter(|| run(i));
}