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day 16

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Acvaxoort
2023-12-16 12:27:24 +01:00
parent f80d4f41f4
commit 90ffdd2029
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day16/src/main.rs Normal file
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use std::fs::read_to_string;
use std::time::Instant;
#[derive(Copy, Clone)]
enum Direction {
Left = 0,
Right = 1,
Up = 2,
Down = 3,
}
const DIRECTION_MASK: [u8; 4] = [1, 2, 4, 8];
fn pass_light(layout: &Vec<&[u8]>, energized: &mut Vec<Vec<u8>>, mut x: usize, mut y: usize, mut dir: Direction) {
loop {
let energized_field = &mut energized[y][x];
let mask = DIRECTION_MASK[dir as usize];
if *energized_field & mask != 0 {
return;
}
*energized_field |= mask;
match dir {
Direction::Left => {
match layout[y][x] {
b'/' => {
if y < layout.len() - 1 {
y += 1;
dir = Direction::Down;
} else {
break;
}
}
b'\\' => {
if y > 0 {
y -= 1;
dir = Direction::Up;
} else {
break;
}
}
b'|' => {
if y > 0 {
pass_light(layout, energized, x, y - 1, Direction::Up);
}
if y < layout.len() - 1 {
pass_light(layout, energized, x, y + 1, Direction::Down);
}
}
_ => {
if x > 0 {
x -= 1;
} else {
break;
}
}
}
}
Direction::Right => {
match layout[y][x] {
b'/' => {
if y > 0 {
y -= 1;
dir = Direction::Up;
} else {
break;
}
}
b'\\' => {
if y < layout.len() - 1 {
y += 1;
dir = Direction::Down;
} else {
break;
}
}
b'|' => {
if y > 0 {
pass_light(layout, energized, x, y - 1, Direction::Up);
}
if y < layout.len() - 1 {
pass_light(layout, energized, x, y + 1, Direction::Down);
}
}
_ => {
if x < layout[0].len() - 1 {
x += 1;
} else {
break;
}
}
}
}
Direction::Up => {
match layout[y][x] {
b'/' => {
if x < layout[0].len() - 1 {
x += 1;
dir = Direction::Right;
} else {
break;
}
}
b'\\' => {
if x > 0 {
x -= 1;
dir = Direction::Left;
} else {
break;
}
}
b'-' => {
if x > 0 {
pass_light(layout, energized, x - 1, y, Direction::Left);
}
if x < layout[0].len() - 1 {
pass_light(layout, energized, x + 1, y, Direction::Right);
}
}
_ => {
if y > 0 {
y -= 1;
} else {
break;
}
}
}
}
Direction::Down => {
match layout[y][x] {
b'/' => {
if x > 0 {
x -= 1;
dir = Direction::Left;
} else {
break;
}
}
b'\\' => {
if x < layout[0].len() - 1 {
x += 1;
dir = Direction::Right;
} else {
break;
}
}
b'-' => {
if x > 0 {
pass_light(layout, energized, x - 1, y, Direction::Left);
}
if x < layout[0].len() - 1 {
pass_light(layout, energized, x + 1, y, Direction::Right);
}
}
_ => {
if y < layout.len() - 1 {
y += 1;
} else {
break;
}
}
}
}
}
}
}
fn main() {
let time_start = Instant::now();
let input_str = read_to_string("input.txt").unwrap();
let time_start_no_io = Instant::now();
let layout = input_str.lines().map(|str| str.as_bytes()).collect::<Vec<_>>();
let mut energized: Vec<Vec<u8>> = vec![vec![0; layout[0].len()]; layout.len()];
pass_light(&layout, &mut energized, 0, 0, Direction::Right);
let count1 = energized.iter().fold(
0, |acc, elem| acc + elem.iter().fold(
0, |acc, &elem| acc + (elem > 0) as i32));
let count2 =
(0..layout.len()).map(|y| (0, y, Direction::Right))
.chain((0..layout.len()).map(|y| (layout[0].len() - 1, y, Direction::Left)))
.chain((0..layout[0].len()).map(|x| (x, 0, Direction::Down)))
.chain((0..layout[0].len()).map(|x| (x, layout.len() - 1, Direction::Up)))
.map(|(x, y, dir)| {
energized.iter_mut().for_each(|vec| vec.iter_mut().for_each(|x| { *x = 0; }));
pass_light(&layout, &mut energized, x, y, dir);
energized.iter().fold(
0, |acc, elem| acc + elem.iter().fold(
0, |acc, &elem| acc + (elem > 0) as i32))
}).max().unwrap();
let elapsed = time_start.elapsed().as_micros();
let elapsed_no_io = time_start_no_io.elapsed().as_micros();
println!("Time: {}us", elapsed);
println!("Time without file i/o: {}us", elapsed_no_io);
println!("Energized1: {}", count1);
println!("Energized2: {}", count2);
}