Day 20

Cargo.toml

@@ -78,3 +78,7 @@ path = "src/day18.rs"
 [[bin]]
 name = "day19"
 path = "src/day19.rs"
+
+[[bin]]
+name = "day20"
+path = "src/day20.rs"

inputs/day20.txt

@@ -0,0 +1,102 @@
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+
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src/day18.rs

@@ -29,14 +29,14 @@ impl Value {
     fn number(&self) -> Option<u32> {
         match self {
             Self::Number(n, _) => Some(*n),
-            _ => None
+            _ => None,
         }
     }
 
     fn index(&self) -> Option<usize> {
         match self {
             Self::Number(_, i) => Some(*i),
-            _ => None
+            _ => None,
         }
     }
 
@@ -104,8 +104,7 @@ fn find_exploded(tree: &Value, depth: usize) -> Option<&Value> {
         if depth == 4 && tree.is_number_pair() {
             Some(tree)
         } else {
-            find_exploded(left, depth + 1)
+            find_exploded(left, depth + 1).or_else(|| find_exploded(right, depth + 1))
-                .or_else(|| find_exploded(right, depth + 1))
         }
     } else {
         None
@@ -114,11 +113,13 @@ fn find_exploded(tree: &Value, depth: usize) -> Option<&Value> {
 
 fn find_number(tree: &mut Value, index: usize, n: u32) -> Option<&Value> {
     match tree {
-        Value::Pair(left, right) => find_number(left, index, n).or_else(|| find_number(right, index, n)),
+        Value::Pair(left, right) => {
+            find_number(left, index, n).or_else(|| find_number(right, index, n))
+        }
         Value::Number(_, i) if *i == index => {
             tree.add_number(n);
             Some(tree)
-        },
+        }
         _ => None,
     }
 }

src/day19.rs

@@ -17,15 +17,16 @@ impl FromStr for Report {
 
 fn make_diffs(reports: &Vec<Report>) -> HashSet<Report> {
     let mut set = HashSet::new();
-    for (i, report) in reports.iter().enumerate() {
+    for (i, report) in reports.iter().enumerate() {}
-        
-    }
     set
 }
 
 fn main() {
     const INPUT: &str = include_str!("../inputs/day19.txt");
-    let reports = INPUT.split("\n\n").map(|scanner| scanner.lines().map(|line| line.parse().unwrap()).collect()).collect::<Vec<Vec<Report>>>();
+    let reports = INPUT
+        .split("\n\n")
+        .map(|scanner| scanner.lines().map(|line| line.parse().unwrap()).collect())
+        .collect::<Vec<Vec<Report>>>();
     let diffs: Vec<HashSet<Report>> = reports.iter().map(make_diffs).collect();
     println!("solution {}", diffs.len());
 }

src/day20.rs

@@ -0,0 +1,158 @@
+use std::fmt;
+use std::str::FromStr;
+
+#[derive(Clone)]
+struct Image {
+    image: Vec<Vec<char>>,
+    algorithm: Vec<char>,
+    background: bool,
+}
+
+impl Image {
+    fn is_light(&self, x: i32, y: i32) -> bool {
+        if x < 1 || y < 1 || x as usize > self.image[0].len() || y as usize > self.image.len() {
+            return self.background;
+        }
+        match self.image[(y - 1) as usize][(x - 1) as usize] {
+            '#' => true,
+            '.' => false,
+            p => panic!("invalid pixel '{}'", p),
+        }
+    }
+
+    fn enhance(self) -> Self {
+        let image = (0..self.image.len() + 2)
+            .map(|y| {
+                (0..self.image[0].len() + 2)
+                    .map(|x| {
+                        let mut idx = 0;
+                        if self.is_light(x as i32 - 1, y as i32 - 1) {
+                            idx += 0x100;
+                        }
+                        if self.is_light(x as i32, y as i32 - 1) {
+                            idx += 0x080;
+                        }
+                        if self.is_light(x as i32 + 1, y as i32 - 1) {
+                            idx += 0x040;
+                        }
+                        if self.is_light(x as i32 - 1, y as i32) {
+                            idx += 0x020;
+                        }
+                        if self.is_light(x as i32, y as i32) {
+                            idx += 0x010;
+                        }
+                        if self.is_light(x as i32 + 1, y as i32) {
+                            idx += 0x008;
+                        }
+                        if self.is_light(x as i32 - 1, y as i32 + 1) {
+                            idx += 0x004;
+                        }
+                        if self.is_light(x as i32, y as i32 + 1) {
+                            idx += 0x002;
+                        }
+                        if self.is_light(x as i32 + 1, y as i32 + 1) {
+                            idx += 0x001;
+                        }
+                        self.algorithm[idx]
+                    })
+                    .collect()
+            })
+            .collect();
+        let background = if self.algorithm[0] == '#' {
+            !self.background
+        } else {
+            false
+        };
+        Image {
+            image,
+            algorithm: self.algorithm,
+            background,
+        }
+    }
+
+    fn light_pixels(self) -> usize {
+        let result = self.enhance().enhance();
+        result
+            .image
+            .iter()
+            .map(|row| row.iter().filter(|p| **p == '#').count())
+            .sum()
+    }
+
+    fn super_light_pixels(self) -> usize {
+        let mut image = self;
+        for _ in 0..50 {
+            image = image.enhance();
+        }
+        image
+            .image
+            .iter()
+            .map(|row| row.iter().filter(|p| **p == '#').count())
+            .sum()
+    }
+}
+
+impl FromStr for Image {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let (algorithm, image) = s.split_once("\n\n").unwrap();
+        let algorithm = algorithm.chars().collect();
+        let image = image
+            .lines()
+            .map(|line| line.trim_end().chars().collect())
+            .collect();
+        Ok(Image {
+            image,
+            algorithm,
+            background: false,
+        })
+    }
+}
+
+impl fmt::Debug for Image {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        writeln!(
+            f,
+            "algorithm: {}\n",
+            self.algorithm.iter().collect::<String>()
+        )?;
+        for row in self.image.iter() {
+            writeln!(f, "{}", row.iter().collect::<String>())?;
+        }
+        Ok(())
+    }
+}
+
+fn main() {
+    const INPUT: &str = include_str!("../inputs/day20.txt");
+    let image: Image = INPUT.parse().unwrap();
+    println!("solution {}", image.clone().light_pixels());
+    println!("solution {}", image.super_light_pixels());
+}
+
+#[test]
+fn test_light_pixels() {
+    const INPUT: &str = "..#.#..#####.#.#.#.###.##.....###.##.#..###.####..#####..#....#..#..##..###..######.###...####..#..#####..##..#.#####...##.#.#..#.##..#.#......#.###.######.###.####...#.##.##..#..#..#####.....#.#....###..#.##......#.....#..#..#..##..#...##.######.####.####.#.#...#.......#..#.#.#...####.##.#......#..#...##.#.##..#...##.#.##..###.#......#.#.......#.#.#.####.###.##...#.....####.#..#..#.##.#....##..#.####....##...##..#...#......#.#.......#.......##..####..#...#.#.#...##..#.#..###..#####........#..####......#..#
+
+#..#.
+#....
+##..#
+..#..
+..###";
+    let image: Image = INPUT.parse().unwrap();
+    assert_eq!(image.light_pixels(), 35);
+}
+
+#[test]
+fn test_super_light_pixels() {
+    const INPUT: &str = "..#.#..#####.#.#.#.###.##.....###.##.#..###.####..#####..#....#..#..##..###..######.###...####..#..#####..##..#.#####...##.#.#..#.##..#.#......#.###.######.###.####...#.##.##..#..#..#####.....#.#....###..#.##......#.....#..#..#..##..#...##.######.####.####.#.#...#.......#..#.#.#...####.##.#......#..#...##.#.##..#...##.#.##..###.#......#.#.......#.#.#.####.###.##...#.....####.#..#..#.##.#....##..#.####....##...##..#...#......#.#.......#.......##..####..#...#.#.#...##..#.#..###..#####........#..####......#..#
+
+#..#.
+#....
+##..#
+..#..
+..###";
+    let image: Image = INPUT.parse().unwrap();
+    assert_eq!(image.super_light_pixels(), 3351);
+}