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|
use nom::{
branch::alt,
character::complete::{char as nom_char, line_ending},
combinator::{map, map_res, value},
multi::{many1, separated_list1},
sequence::tuple,
IResult,
};
use std::{collections::BTreeSet, fs};
fn main() -> Result<(), Box<dyn std::error::Error>> {
let input = fs::read_to_string("inputs/day_20.txt")?;
let mut enhanceable_image = parse_enhanceable_image(&input).unwrap().1;
for _ in 0..2 {
enhanceable_image = enhanceable_image.enhance();
}
dbg!(enhanceable_image.image.count_light_spots().unwrap());
for _ in 2..50 {
enhanceable_image = enhanceable_image.enhance();
}
dbg!(enhanceable_image.image.count_light_spots().unwrap());
Ok(())
}
#[derive(Debug)]
struct EnhanceableImage {
enhancement_lights: [bool; 512],
image: Image,
}
impl EnhanceableImage {
fn enhance(&self) -> EnhanceableImage {
let current_background_dark = matches!(self.image, Image::LightSpots(_));
let next_background_dark =
!self.enhancement_lights[if current_background_dark { 0 } else { 511 }];
let mut spots = BTreeSet::new();
let top_left = self.image.top_left(1);
let bottom_right = self.image.bottom_right(1);
for y in top_left.y..=bottom_right.y {
for x in top_left.x..=bottom_right.x {
let center = Point { x, y };
let surrounds = center.surrounds();
let number = self.image.to_number(surrounds);
let center_is_light = self.enhancement_lights[number];
if center_is_light == next_background_dark {
spots.insert(center);
}
}
}
EnhanceableImage {
enhancement_lights: self.enhancement_lights.clone(),
image: if next_background_dark {
Image::LightSpots(spots)
} else {
Image::DarkSpots(spots)
},
}
}
}
#[derive(Debug)]
enum Image {
LightSpots(BTreeSet<Point>),
DarkSpots(BTreeSet<Point>),
}
#[derive(Debug)]
enum ImageError {
InfiniteLight,
}
impl Image {
fn count_light_spots(&self) -> Result<usize, ImageError> {
match self {
Self::LightSpots(spots) => Ok(spots.len()),
Self::DarkSpots(_) => Err(ImageError::InfiniteLight),
}
}
fn top_left(&self, margin: i32) -> Point {
let (Self::LightSpots(spots) | Self::DarkSpots(spots)) = self;
let min_x = spots.iter().map(|p| p.x).min().unwrap_or(0);
let min_y = spots.iter().map(|p| p.y).min().unwrap_or(0);
Point {
x: min_x - margin,
y: min_y - margin,
}
}
fn bottom_right(&self, margin: i32) -> Point {
let (Self::LightSpots(spots) | Self::DarkSpots(spots)) = self;
let max_x = spots.iter().map(|p| p.x).max().unwrap_or(0);
let max_y = spots.iter().map(|p| p.y).max().unwrap_or(0);
Point {
x: max_x + margin,
y: max_y + margin,
}
}
fn to_number(&self, bit_locations: [Point; 9]) -> usize {
let mut result = 0;
for bit_location in bit_locations {
result <<= 1;
let next_is_1 = match self {
Self::LightSpots(spots) => spots.contains(&bit_location),
Self::DarkSpots(spots) => !spots.contains(&bit_location),
};
if next_is_1 {
result += 1;
}
}
result
}
}
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
struct Point {
x: i32,
y: i32,
}
impl Point {
fn surrounds(&self) -> [Point; 9] {
[
Point {
x: self.x - 1,
y: self.y - 1,
},
Point {
x: self.x,
y: self.y - 1,
},
Point {
x: self.x + 1,
y: self.y - 1,
},
Point {
x: self.x - 1,
y: self.y,
},
Point {
x: self.x,
y: self.y,
},
Point {
x: self.x + 1,
y: self.y,
},
Point {
x: self.x - 1,
y: self.y + 1,
},
Point {
x: self.x,
y: self.y + 1,
},
Point {
x: self.x + 1,
y: self.y + 1,
},
]
}
}
fn parse_enhanceable_image(input: &str) -> IResult<&str, EnhanceableImage> {
map(
tuple((parse_enhancement_lights, many1(line_ending), parse_image)),
|(enhancement_lights, _, image)| EnhanceableImage {
enhancement_lights,
image,
},
)(input)
}
fn parse_enhancement_lights(input: &str) -> IResult<&str, [bool; 512]> {
map_res(many1(parse_pixel), |pixels| pixels.try_into())(input)
}
fn parse_image(input: &str) -> IResult<&str, Image> {
map(separated_list1(line_ending, many1(parse_pixel)), |pixels| {
let mut result = BTreeSet::new();
for (y, row) in pixels.into_iter().enumerate() {
for (x, light) in row.into_iter().enumerate() {
if light {
result.insert(Point {
x: x as i32,
y: y as i32,
});
}
}
}
Image::LightSpots(result)
})(input)
}
fn parse_pixel(input: &str) -> IResult<&str, bool> {
alt((value(true, nom_char('#')), value(false, nom_char('.'))))(input)
}
|
