Day 20 part 1 w/ hack

2021/src/day20.rs

@@ -0,0 +1,170 @@
+use advent::prelude::*;
+use aoc_runner_derive::aoc;
+
+struct Image(HashSet<(isize, isize)>);
+
+impl Image {
+    fn new(input: &str) -> Image {
+        let rows: Vec<_> = input.lines().collect();
+        let width = rows[0].len();
+        Image(
+            rows.iter()
+                .flat_map(|row| row.as_bytes().iter())
+                .enumerate()
+                .filter(|(_i, b)| *b == &b'#')
+                .map(|(i, _b)| ((i % width) as isize, (i / width) as isize))
+                .collect(),
+        )
+    }
+    fn lookup(&self, x: isize, y: isize, algo: &[bool]) -> usize {
+        assert_eq!(algo.len(), 512);
+        let mut idx = 0;
+        for y_off in -1..=1 {
+            for x_off in -1..=1 {
+                idx <<= 1;
+                let x_idx = x + x_off;
+                let y_idx = y + y_off;
+                idx |= if self.0.contains(&(x_idx, y_idx)) {
+                    1
+                } else {
+                    0
+                };
+            }
+        }
+        idx
+    }
+    fn extents(&self) -> (isize, isize, isize, isize) {
+        self.0.iter().fold(
+            (isize::MAX, isize::MIN, isize::MAX, isize::MIN),
+            |(min_x, max_x, min_y, max_y), (x, y)| {
+                (min_x.min(*x), max_x.max(*x), min_y.min(*y), max_y.max(*y))
+            },
+        )
+    }
+
+    fn enhance(&self, algo: &[bool]) -> Image {
+        let (min_x, max_x, min_y, max_y) = self.extents();
+        let mut new_im = HashSet::new();
+        for y in min_y - 10..=max_y + 10 {
+            for x in min_x - 10..=max_x + 10 {
+                let idx = self.lookup(x, y, algo);
+                if algo[idx] {
+                    new_im.insert((x, y));
+                }
+            }
+        }
+        Image(new_im)
+    }
+
+    fn lights(&self) -> usize {
+        self.0.len()
+    }
+    fn crop(&self, min_x: isize, max_x: isize, min_y: isize, max_y: isize) -> Image {
+        let x_rng = min_x..=max_x;
+        let y_rng = min_y..=max_y;
+        Image(
+            self.0
+                .iter()
+                .filter(|(x, y)| x_rng.contains(x) && y_rng.contains(y))
+                .cloned()
+                .collect(),
+        )
+    }
+}
+
+impl Debug for Image {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
+        let (min_x, max_x, min_y, max_y) = self.extents();
+        writeln!(f, "({}..{})x({}..{})", min_x, max_x, min_y, max_y)?;
+        for y in min_y..=max_y {
+            for x in min_x..=max_x {
+                if self.0.contains(&(x, y)) {
+                    write!(f, "#")?;
+                } else {
+                    write!(f, ".")?;
+                }
+            }
+            writeln!(f)?;
+        }
+        Ok(())
+    }
+}
+
+#[aoc(day20, part1)]
+fn part1(input: &str) -> Result<usize> {
+    let (algo, im) = input.split_once("\n\n").unwrap();
+    let im = Image::new(im);
+    let algo: Vec<bool> = algo.as_bytes().iter().map(|c| c == &b'#').collect();
+
+    let (min_x, max_x, min_y, max_y) = im.extents();
+
+    dbg!(&im, im.lights());
+    let im = im.enhance(&algo);
+    dbg!(&im, im.lights());
+    let im = im.enhance(&algo);
+    dbg!(&im, im.lights());
+    let im = im.crop(min_x - 2, max_x + 2, min_y - 2, max_y + 2);
+    dbg!(&im, im.lights());
+    let answer = im.lights();
+    assert!(answer < 5285);
+    Ok(answer)
+}
+
+/*
+#[aoc(day20, part2)]
+fn part2(input: &str) -> Result<usize> {
+todo!("part2");
+Ok(0)
+}
+*/
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn lookup() -> Result<()> {
+        let input = r#"
+..#.#..#####.#.#.#.###.##.....###.##.#..###.####..#####..#....#..#..##..###..######.###...####..#..#####..##..#.#####...##.#.#..#.##..#.#......#.###.######.###.####...#.##.##..#..#..#####.....#.#....###..#.##......#.....#..#..#..##..#...##.######.####.####.#.#...#.......#..#.#.#...####.##.#......#..#...##.#.##..#...##.#.##..###.#......#.#.......#.#.#.####.###.##...#.....####.#..#..#.##.#....##..#.####....##...##..#...#......#.#.......#.......##..####..#...#.#.#...##..#.#..###..#####........#..####......#..#
+
+#..#.
+#....
+##..#
+..#..
+..###
+"#
+.trim();
+        let (algo, im) = input.split_once("\n\n").unwrap();
+        let im = Image::new(im);
+        let algo: Vec<bool> = algo.as_bytes().iter().map(|c| c == &b'#').collect();
+        assert_eq!(im.lookup(2, 2, &algo), 34);
+        Ok(())
+    }
+
+    #[test]
+    fn test_part1() -> Result<()> {
+        let input = r#"
+..#.#..#####.#.#.#.###.##.....###.##.#..###.####..#####..#....#..#..##..###..######.###...####..#..#####..##..#.#####...##.#.#..#.##..#.#......#.###.######.###.####...#.##.##..#..#..#####.....#.#....###..#.##......#.....#..#..#..##..#...##.######.####.####.#.#...#.......#..#.#.#...####.##.#......#..#...##.#.##..#...##.#.##..###.#......#.#.......#.#.#.####.###.##...#.....####.#..#..#.##.#....##..#.####....##...##..#...#......#.#.......#.......##..####..#...#.#.#...##..#.#..###..#####........#..####......#..#
+
+#..#.
+#....
+##..#
+..#..
+..###
+"#
+.trim();
+        assert_eq!(part1(input)?, 35);
+        Ok(())
+    }
+
+    /*
+    #[test]
+    fn test_part2()->Result<()> {
+    let input = r#"
+    "#
+    .trim();
+    assert_eq!(part2(input)?, usize::MAX);
+    Ok(())
+    }
+    */
+}

2021/src/lib.rs

@@ -7,8 +7,9 @@ pub mod day13;
 pub mod day15;
 pub mod day16;
 pub mod day17;
-pub mod day18;
+//pub mod day18;
 pub mod day2;
+pub mod day20;
 pub mod day3;
 pub mod day4;
 pub mod day5;