feat: solve day 20 part 1 & 2

input/20.txt

@@ -0,0 +1,102 @@
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src/day20.rs

@@ -0,0 +1,235 @@
+use std::{ops::Range, fmt::Display};
+
+
+#[derive(Clone, Debug)]
+pub struct Image {
+    width: usize,
+    height: usize,
+    data: Vec<bool>,
+    default_value: bool,
+    offset_x: i32,
+    offset_y: i32
+}
+
+impl Image {
+    fn new(width: usize, height: usize) -> Image {
+        let data = vec![false; width*height];
+        Image {
+            width,
+            height,
+            data,
+            default_value: false,
+            offset_x: 0,
+            offset_y: 0
+        }
+    }
+
+    fn get(&self, x: i32, y: i32) -> bool {
+        if self.in_bounds(x, y) {
+            let index = (y + self.offset_y) * self.width as i32 + (x + self.offset_x);
+            *self.data.get(index as usize).unwrap_or(&self.default_value)
+        } else {
+            self.default_value
+        }
+    }
+
+    fn set(&mut self, x: i32, y: i32, value: bool) {
+        // Make image larger if it is too small
+        let (left, top, right, bottom) = self.bounds();
+        if !(left <= x && x < right && top <= y && y < bottom) {
+            if x < left {
+                self.offset_x = -x;
+                self.width = self.width + (-x + left) as usize;
+            } else if x >= right {
+                self.width = self.width + 1 + (x - right) as usize;
+            }
+
+            if y < top {
+                self.offset_y = -y;
+                self.height = self.height + (-y + top) as usize;
+            } else if y >= bottom {
+                self.height = self.height + 1 + (y - bottom) as usize;
+            }
+
+            let mut new_data = Vec::new();
+            for y in self.y_range(0) {
+                for x in self.x_range(0) {
+                    new_data.push(self.get(x, y));
+                }
+            }
+            self.data = new_data;
+        }
+
+        let index = ((y + self.offset_y) * self.width as i32 + (x + self.offset_x)) as usize;
+        self.data[index] = value;
+    }
+
+    fn in_bounds(&self, x: i32, y: i32) -> bool {
+        let (left, top, right, bottom) = self.bounds();
+        left <= x && x < right && top <= y && y < bottom
+    }
+
+    fn count(&self, value: bool) -> usize {
+        if self.default_value == value {
+            usize::MAX
+        } else {
+            self.data.iter().filter(|x| **x == value).count()
+        }
+    }
+
+    fn x_range(&self, padding: u32) -> Range<i32> {
+        let padding = padding as i32;
+        Range {
+            start: -self.offset_x - padding,
+            end: self.width as i32 - self.offset_x + padding
+        }
+    }
+
+    fn y_range(&self, padding: u32) -> Range<i32> {
+        let padding = padding as i32;
+        Range {
+            start: -self.offset_y - padding,
+            end: self.height as i32 - self.offset_y + padding
+        }
+    }
+
+    // (i32, i32, i32, i32) => (left, top, right, bottom)
+    fn bounds(&self) -> (i32, i32, i32, i32) {
+        return (
+            -self.offset_x,
+            -self.offset_y,
+            self.width as i32 - self.offset_x,
+            self.height as i32 - self.offset_y
+        );
+    }
+}
+
+impl Display for Image {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let mut grid = String::new();
+        for y in self.y_range(1) {
+            for x in self.x_range(1) {
+                let symbol = if self.get(x, y) { '#' } else { '.' };
+                grid.push(symbol);
+            }
+            grid.push('\n');
+        }
+        write!(f, "{}", grid)
+    }
+}
+
+fn parse_image(input: &str) -> Image {
+    let mut image = Image::new(3, 3);
+    let mut y = 0;
+    for line in input.lines() {
+        let mut x = 0;
+        for c in line.chars() {
+            image.set(x, y, c == '#');
+            x += 1;
+        }
+        y += 1
+    }
+    return image;
+}
+
+fn parse_enchancer(input: &str) -> [bool; 512] {
+    let mut enhancer = [false; 512];
+    let mut i = 0;
+    for c in input.chars() {
+        enhancer[i] = c == '#';
+        i+=1;
+    }
+    return enhancer
+}
+
+pub fn parse_input(input: &str) -> ([bool; 512], Image) {
+    let (section1, section2) = input.split_once("\n\n").unwrap();
+    return (
+        parse_enchancer(section1),
+        parse_image(section2)
+    );
+}
+
+fn lookup_enhancer(x: i32, y: i32, image: &Image, enhancer: &[bool; 512]) -> bool {
+    let pixel_offsets = [
+        (-1, -1), ( 0, -1), ( 1, -1),
+        (-1,  0), ( 0,  0), ( 1,  0),
+        (-1,  1), ( 0,  1), ( 1,  1)
+    ];
+
+    let mut lookup_index = 0;
+    for i in 0..9 {
+        let (ox, oy) = pixel_offsets[i];
+        let pixel = image.get(x + ox, y + oy);
+        if pixel {
+            lookup_index += 2usize.pow((8-i) as u32)
+        }
+    }
+
+    enhancer[lookup_index]
+}
+
+fn enhance(image: &Image, enhancer: &[bool; 512]) -> Image {
+    let mut enhanced = image.clone();
+    for y in image.y_range(1) {
+        for x in image.x_range(1) {
+            enhanced.set(x, y, lookup_enhancer(x, y, image, enhancer));
+        }
+    }
+
+    if image.default_value {
+        enhanced.default_value = enhancer[511];
+    } else {
+        enhanced.default_value = enhancer[0];
+    }
+
+    enhanced
+}
+
+pub fn part1(data: &([bool; 512], Image)) -> usize {
+    let (enhancer, image) = data;
+    let mut enhanced_image = enhance(&image, enhancer);
+    enhanced_image = enhance(&enhanced_image, enhancer);
+    enhanced_image.count(true)
+}
+
+pub fn part2(data: &([bool; 512], Image)) -> usize {
+    let (enhancer, image) = data;
+    let mut enhanced_image = enhance(&image, enhancer);
+    for _ in 0..49 {
+        enhanced_image = enhance(&enhanced_image, enhancer);
+    }
+    enhanced_image.count(true)
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example() {
+        let input = parse_input("..#.#..#####.#.#.#.###.##.....###.##.#..###.####..#####..#....#..#..##..###..######.###...####..#..#####..##..#.#####...##.#.#..#.##..#.#......#.###.######.###.####...#.##.##..#..#..#####.....#.#....###..#.##......#.....#..#..#..##..#...##.######.####.####.#.#...#.......#..#.#.#...####.##.#......#..#...##.#.##..#...##.#.##..###.#......#.#.......#.#.#.####.###.##...#.....####.#..#..#.##.#....##..#.####....##...##..#...#......#.#.......#.......##..####..#...#.#.#...##..#.#..###..#####........#..####......#..#
+
+#..#.
+#....
+##..#
+..#..
+..###");
+        let result = part1(&input);
+        assert_eq!(result, 35);
+    }
+
+    #[test]
+    fn part2_example() {
+        let input = parse_input("..#.#..#####.#.#.#.###.##.....###.##.#..###.####..#####..#....#..#..##..###..######.###...####..#..#####..##..#.#####...##.#.#..#.##..#.#......#.###.######.###.####...#.##.##..#..#..#####.....#.#....###..#.##......#.....#..#..#..##..#...##.######.####.####.#.#...#.......#..#.#.#...####.##.#......#..#...##.#.##..#...##.#.##..###.#......#.#.......#.#.#.####.###.##...#.....####.#..#..#.##.#....##..#.####....##...##..#...#......#.#.......#.......##..####..#...#.#.#...##..#.#..###..#####........#..####......#..#
+
+#..#.
+#....
+##..#
+..#..
+..###");
+        let result = part2(&input);
+        assert_eq!(result, 3351);
+    }
+}

src/main.rs

@@ -72,6 +72,8 @@ fn run(day: i32, part: i32, input_filename: &str) {
         "18.2" => println!("{}", day18::part2(&day18::parse_input(&contents))),
         "19.1" => println!("{}", day19::part1(&day19::parse_input(&contents))),
         "19.2" => println!("{}", day19::part2(&day19::parse_input(&contents))),
+        "20.1" => println!("{}", day20::part1(&day20::parse_input(&contents))),
+        "20.2" => println!("{}", day20::part2(&day20::parse_input(&contents))),
         _ => println!("Day {} part {} not found", day, part)
     }
 }
@@ -97,4 +99,3 @@ fn main() {
     }
     run(day, part, &input_filename);
 }
-