bendns' repos / aoc
heh
Diffstat (limited to 'src/main.rs')
-rw-r--r--src/main.rs85
1 files changed, 28 insertions, 57 deletions
diff --git a/src/main.rs b/src/main.rs
index 6926456..fea8e8f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -9,69 +9,40 @@
)]
extern crate test;
mod util;
-pub use util::prelude::*;
+use std::mem::ManuallyDrop;
-#[inline(always)]
-fn k(s: &[u8]) -> u16 {
- unsafe { *s.as_ptr().cast::<[u8; 3]>() }
- .iter()
- .enumerate()
- .map(|(i, &b)| ((b - b'A') as u16) << (i * 5))
- .sum()
-}
+pub use util::prelude::*;
-fn start(x: u16) -> bool {
- (x >> (2 * 5) & 0b11111) == 0u16
+pub fn p1(a: &[i32]) -> i32 {
+ if !a[1..].iter().any(|&x| x != a[0]) {
+ a[0]
+ } else {
+ *a.last().unwrap()
+ + p1(&*ManuallyDrop::new(
+ a.array_windows::<2>()
+ .map(|[b, a]| a - b)
+ .collect::<Box<[_]>>(),
+ ))
+ }
}
-fn end(x: u16) -> bool {
- (x >> (2 * 5) & 0b11111) == (b'Z' - b'A') as u16
+pub fn p2(a: &[i32]) -> i32 {
+ if !a[1..].iter().any(|&x| x != a[0]) {
+ a[0]
+ } else {
+ *a.first().unwrap()
+ - p2(&*ManuallyDrop::new(
+ a.array_windows::<2>()
+ .map(|[b, a]| a - b)
+ .collect::<Box<[_]>>(),
+ ))
+ }
}
-pub fn run(mut i: &str) -> impl Display {
- let line = i.take_line().unwrap();
- let map = i
- .as_bytes()
- .array_chunks::<17>()
- .map(|x| (k(&x[1..4]), (k(&x[8..11]), k(&x[13..16]))))
- .collect::<HashMap<_, _>>();
- let mut positions = map
- .keys()
- .map(|&x| x)
- .filter(|&x| start(x))
- .collect::<Box<[_]>>();
- let mut steps = 1u64;
- let mut findings = HashMap::new();
- let mut cycle = HashMap::new();
- for &instruction in line.iter().cycle() {
- if cycle.len() >= positions.len() {
- break;
- }
- for p in &mut *positions {
- let at = map[p];
- *p = match instruction {
- b'L' => at.0,
- b'R' => at.1,
- _ => dang!(),
- };
- if end(*p) {
- if let Some(&c) = findings.get(p) {
- match cycle.entry(*p) {
- Entry::Occupied(_) => {}
- Entry::Vacant(x) => {
- x.insert(steps - c);
- }
- }
- } else {
- findings.insert(*p, steps);
- }
- }
- }
- steps += 1;
- }
- let v = lcm(cycle.values().copied());
- leek!(cycle findings positions);
- v
+pub fn run(i: &str) -> impl Display {
+ i.行()
+ .map(|x| p1(&*ManuallyDrop::new(x.κ().collect::<Box<[i32]>>())))
+ .sum::<i32>()
}
fn main() {