bendns' repos / aoc
heh
Diffstat (limited to 'src/main.rs')
-rw-r--r--src/main.rs100
1 files changed, 46 insertions, 54 deletions
diff --git a/src/main.rs b/src/main.rs
index 3095717..5fd542c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -36,64 +36,56 @@ pub mod util;
pub use util::prelude::*;
const SIZE: usize = 140;
-fn explore(
- (x, y): (usize, usize),
- handled: &mut [[bool; 140]; 140],
- char: u8,
- get: &mut impl FnMut(usize, usize) -> Option<u8>,
- tot: &mut u32,
- count: &mut u32,
-) {
- if get(x, y) == Some(char) && handled[y][x] == false {
- handled[y][x] = true;
- // αbβ
- // a.c
- // γdδ
- let α = get(x.wrapping_sub(1), y.wrapping_sub(1)) != Some(char);
- let β = get(x.wrapping_add(1), y.wrapping_sub(1)) != Some(char);
- let γ = get(x.wrapping_sub(1), y.wrapping_add(1)) != Some(char);
- let δ = get(x.wrapping_add(1), y.wrapping_add(1)) != Some(char);
-
- let a = get(x.wrapping_sub(1), y) != Some(char);
- let b = get(x, y.wrapping_sub(1)) != Some(char);
- let c = get(x.wrapping_add(1), y) != Some(char);
- let d = get(x, y.wrapping_add(1)) != Some(char);
- fn u(a: bool) -> u32 {
- a as u32
- }
- // *tot += u(a) + u(b) + u(c) + u(d);
-
- *tot += u(a & b) + u(b & c) + u(c & d) + u(a & d);
- *tot += u(!a & !b & α) + u(!b & !c & β) + u(!c & !d & δ) + u(!a & !d & γ);
- *count += 1;
-
- explore((x.wrapping_sub(1), y), handled, char, get, tot, count);
- explore((x + 1, y), handled, char, get, tot, count);
- explore((x, y + 1), handled, char, get, tot, count);
- explore((x, y.wrapping_sub(1)), handled, char, get, tot, count);
- }
+fn two([a, b]: [u8; 2]) -> i64 {
+ (a - b'0') as i64 * 10 + (b - b'0') as i64
}
#[no_mangle]
pub fn run(i: &str) -> impl Display {
- let grid = unsafe { i.as_bytes().as_chunks_unchecked::<{ SIZE + 1 }>() };
- let handled = &mut [[false; SIZE]; SIZE];
- let mut get = |x: usize, y: usize| {
- unsafe { core::hint::assert_unchecked(grid.len() == SIZE) };
- (x < SIZE && y < SIZE).then(|| grid[y][x])
- };
- (0..SIZE)
- .flat_map(move |y| (0..SIZE).map(move |x| (x, y)))
- .filter_map(|(x, y)| {
- let mut sides = 0;
- let mut area = 0;
- (!handled[y][x]).then(|| {
- let char = C! { grid[y][x]};
- explore((x, y), handled, char, &mut get, &mut sides, &mut area);
- area * sides
- })
- })
- .sum::<u32>()
+ let mut i = i.as_bytes();
+ // let i = i.as_chunks_unchecked::<{ SIZE + 1 }>();
+ // let get = |x, y| (x < SIZE && y < SIZE).then(|| i[y][x]);
+ let mut sum = 0;
+ loop {
+ i.skip_n("button a: x+");
+ let a_x = two(i.rd::<2>().ψ());
+ i.skip_n(", y+");
+ let a_y = two(i.rd::<2>().ψ());
+ i.skip_n("\nbutton b: x+");
+ let b_x = two(i.rd::<2>().ψ());
+ i.skip_n(", y+");
+ let b_y = two(i.rd::<2>().ψ());
+ i.skip_n("\nprize: x=");
+ let p_x: i64 = reading::until(&mut i, b',');
+ i.skip_n(" y=");
+ let p_y: i64 = reading::until(&mut i, b'\n');
+
+ #[inline]
+ fn dmod(a: i64, b: i64) -> (i64, i64) {
+ (a / b, a % b)
+ }
+ // a_x * α + b_x * β = p_x
+ // a_y * α + b_y * β = p_y
+ let (α, ok) = dmod(
+ b_y * p_x - b_x * p_y, //
+ a_x * b_y - a_y * b_x,
+ );
+ if ok == 0 {
+ let (β, ok) = dmod(
+ a_y * p_x - a_x * p_y, //
+ a_y * b_x - a_x * b_y,
+ );
+ if ok == 0 {
+ sum += 3 * α + β;
+ }
+ }
+
+ if i.is_empty() {
+ break;
+ }
+ i.skip(1);
+ }
+ sum
}
fn main() {