Implementation day 3

2020/inputs/03.txt

@@ -0,0 +1,323 @@
+..#......###....#...##..#.#....
+.#.#.....#.##.....###...##...##
+..#.#..#...........#.#..#......
+..#......#..........###........
+...#..###..##.#..#.......##..##
+......#.#.##...#...#....###....
+..........##.....##..##......#.
+......#...........#............
+#....#..........#..............
+.#........##.............###.##
+....#.........#.......#.#....##
+#.#..#..#..#.......#...#....##.
+.#........#......#.##.......#..
+..#.....#####.....#....#..#..##
+.......#..##.......#......#.###
+..#.#...#......#.##...#........
+##...................#...##..#.
+......#...#.##...##.#......#..#
+.#.................#..##...#...
+...#.....#.......##.....#.#....
+.......#.#......#.....#..#..##.
+..........#........#...........
+..#.#..........................
+.#.##..#.#...#...#.........#...
+.....#....#.....#..#.....#.....
+...#.#.#.....#.#..#.......#..#.
+.....#...###...##...#......##..
+#.###......#.#...#.#.#..###....
+#.....#..##......#..........#.#
+#...............#........#.#..#
+.....#..#.........#......##.#..
+.....#.##.##..#..##............
+...#......##...............#.#.
+.#..#.#............##.#........
+#.....#..###.............##.#..
+...##..#.#..#...........#..#...
+#....#.........#.#.............
+##.#.........#..###......#.#..#
+...#...#......#.#.#.##..#.##...
+.....##............#.##.##..#..
+....#................#.##..#..#
+...#..#.......#...#..#........#
+....#...#...#................#.
+....##...............#.#...#...
+.#.....###...#.......#.##......
+....######.#..............###.#
+.#..#.........##...............
+................##.#..#....###.
+.......#............#.#..#..#..
+......#.#...............##.#...
+...#..####.#...#..#..#......#..
+....#.#...#.....#.........#..##
+.##..#...#......##....##.#.#...
+.##.#.........##...#....#......
+..#.#..#...#.#..#.......#...#.#
+.........#..#.....##..#........
+..#......#..##.....#..#...###..
+..#...#....#.#..#..#.#.#..#.#..
+...#..#####.....#......#.......
+#.#............#......#..#...#.
+.........#..........###.......#
+......#....#..#.##.#......#..#.
+...........##.#....#.#..#......
+..#...................#..#.#...
+#....##.............##....#...#
+##..#....#.........#..........#
+....#.#.#...#..#........#.##..#
+...............#...#..##..#....
+.##.......#.......#...........#
+#.........................##...
+#........#.#..#..##..####.#....
+...................##.....###..
+.#.......#..#......#......#...#
+..#.........#...#..........#...
+..........#......#....#........
+.#......#..#...#..#...##....##.
+...#.#..#..#......#.....##.####
+.......#.#....#.......#........
+#...#.#...##..##.#......#......
+.#.........#...................
+...#..........#.#......#.......
+...#.....##....#..........#....
+.#..........##..#..#..##....#.#
+.##.#..........#...#.##.......#
+#...###....#..#.#...#..#.......
+..................##...........
+..#...##.#...........#....#.##.
+..#......#..##..#....##..#...#.
+..#....#.....#.##..#.......#..#
+#...#....#..#.#....#......##...
+.......##..#..........#........
+..#.............##.#.....#...#.
+...............#....#...#...##.
+##...........#.......#.##......
+#..#...........#.........#.....
+....###.............###.##..##.
+.........#.#.....###.......#...
+..#.##....#.#..........#....#..
+#........#....##...#..#........
+......#..........###..#.#......
+.....#.#......##.....#..##...#.
+.#.......#......#...#...#...#.#
+.#..........##.......#.....##.#
+###.#...#....#.....#...#......#
+..#.#.#..#.##.#..#.............
+.....#.........................
+.#..###..#...#...#..#..#...#.#.
+#................##...##.##....
+......#...#...#..........#...#.
+..........#.....##.............
+..#.#......#........#.......#..
+........##.............#.......
+.......#......#.##.#..#........
+#.#.#....#........#..........#.
+##..##......#..#..#.....#.#..##
+##..#..........#...............
+#.....##...#.#......#.......#.#
+#.....#...#....#..#.....##.....
+##..........#.#.....#....#...##
+..##.###..#.....#.......#...#..
+.#.#.......#......###........#.
+.#..............#.#..###.......
+.#....#..##.........#..#.#.....
+....#....#.#....#..#.......##.#
+#.......#.......#.........#....
+...#....#....#.....##..#..#.#.#
+........#....#...........#.....
+.#......##.#.#.##..............
+#..#.#.....##........#........#
+##...#.#.......##.......#...#..
+#...#.....#.##...##.#.....#....
+....#..##...#........#.#...#...
+...#....#.#.#..###...##.#.....#
+......#..#.....#..#........##..
+.......#.....#.#.........#.#..#
+..#.......#.#.#.#.#....#.##...#
+.#...#........#..##..#......#..
+.#..#............#...#..#.#....
+...##......#......#............
+..#...#.#.....#.....#..##.#....
+.#......#.#......#..#.#........
+..#..........##...#.#.....#..#.
+#...#.....#..#...#.............
+..##.................#....#....
+.#....#.......#..##....#......#
+.#....###............##....##.#
+##..#........#..#...#.......#..
+.....#.....#.#.#.##.........#..
+.......#..#....#...#...#.......
+...#...#...#.#.#..#.#.....#....
+#.#........#..#.##..#..###.....
+..................#..#.........
+#.#.....#..##.........#.......#
+###..#.......#..............#..
+......#..#.....###..........#..
+....#.#...#..#...........#.#...
+...#.....#.......#.....#.#.....
+#.....##..#......##...........#
+#...###...........##..#...#.##.
+......##.##.#...#..#....#......
+...#.#......##.#......##....#.#
+..............#.#.###.......#..
+........#....#.......##..#..###
+...#.....##.#....#......##..#.#
+..##........#.....#.#..#...#...
+.#..#.##.........#.....#...#..#
+..#..#....#...........#........
+.#...#....................#....
+##.....##....#.............#.#.
+....#.#..#.#..#.#.#..........##
+.............##.#.....#..#..#..
+.#....#.....##...#.###.........
+..#........#........#.#..###...
+.##....#...#...#.......#...#.#.
+..#...#...#..##........#..#....
+..##.#..#..#.....#......#.#..#.
+.#........#..#....#..#.........
+..#.#.....#.##..#........###.#.
+.....#.##.....##.#.............
+#.........#.......#...##...#...
+..#.##.#..#..#............#....
+.##....#..#............#.....#.
+###........##.....##.#...#.....
+#......##..##.#.#.#.#.#.#..##..
+.....###.....#....#......#....#
+........#.........##...#....#.#
+.#.#.....#.#..#..##......#...#.
+...#.##....#..#.###..#..##.....
+....#..........##..#..#..#..#..
+...#..#.##..#..#....#.........#
+.....#..###.#.....#.....#..#...
+......#...#....#.##...#.#......
+.#.###..##.....##.##......##...
+.....#.#...........#.#.........
+#........#...#..#......##.#....
+..#.......##....##....#.##.#..#
+...###.#.........#......#.....#
+..#.##..#....#.....##...#.##...
+....##.##.............#...#....
+##..#...#..#..#..#.............
+.....#.....#.....#.............
+...#.##.......#..#.#.....#....#
+#.....##.........#......##.....
+.....##..........#..#...#..#...
+#...###....#.......#...##......
+.#....#..#......#.....#...#.#..
+#........#.#.#...#.....###.#.##
+##...#...##..#..#....#.........
+....#............#..#.....#....
+#......#.........##....#.......
+.#..#..#........#.............#
+.##..........#......#.......#..
+#............#..#....#.........
+....#.#.....#.##...#.....#.#...
+...#.#..#...##..#...#.#.#......
+#....#..#.........##..#.#.#..##
+.#...#..............#.......#..
+#...#.....#.#........##......##
+...#....##.####.#.........#.#.#
+....###.#..#............#.#..#.
+....#......#...#......##.#.#.#.
+.....#..#.#.##.#...##..........
+##..#...#.#...###.............#
+....#...#..#.....#.#..#..#..#..
+#..........####......#.....###.
+.........#........#.##.#...#...
+.........#..........#.#..###...
+.....##........##.........#...#
+..##....#...#.......##.........
+.....#.#......##....#...#...#..
+.##..#..##.....................
+.......#...#..#..#...##....#...
+.#...#.......###...#..#..#.....
+.......#.....##.##.#.......#..#
+.##......#...#....#..#......##.
+.##....#..#....#...#...#.......
+.........##..#..#.#.#.....##...
+...#..............#..#.....####
+.#.#.#..#.......#.......#......
+..#.#......#..........#........
+.#...#.#..#.......#..#..#..#...
+.......##.#...#..#....#.....#..
+.##...##....##...#........####.
+....#.#..##....#...#....#.#....
+.....#.....#..#..#.#.##..#.....
+..#....#..............#....#...
+..#.#.#.....##.#.....#..##.....
+....#.....#....#...#...#..#.#..
+#...#...........#..#..#........
+...#.#..#.........##.#...#..##.
+......#.#.........#.#...#......
+......#..##.###......##.#....#.
+.....#...#..#.......#..........
+.#...#.......#.....###......#..
+...........##.....#..#..#....#.
+..#....#..#...#......#.......#.
+..#...#...#.#..#....#...#......
+.......#....###.####...###.#...
+#.##.#.......#.......#....#.#.#
+.##..........#.....#..###......
+.....#...........#.##..#....#..
+........##.....#.#........##...
+#..#..#..................##....
+#...###..........#.............
+.......#.#.......#.#.......##..
+.....#.#...#....#...####.....#.
+..##.....##.......#....#.......
+##..........#...#..##....##....
+..........#..#......#........#.
+##..#....#..#....#.....##....#.
+##.##.....#...##.##.......#....
+..#..#.###.#..##.#..#..#...#...
+.#..#.....#........#...##.#....
+..#..#.....#.#......##.#.#.....
+.#..##...#.#....#...#...#.#.##.
+.........#...#....###.#.....#..
+...........###.#.#..#..#...#.#.
+##...#......##...........#..#..
+.........##..#...#.......#.....
+#......#.#..........#..#.......
+...#.................#....#....
+#....#......................##.
+##.......#..#......#.#...###.#.
+..#....#..#.#......#...........
+...#...........###.#.#.........
+..#..##.....#.....##...##......
+..#..#.#.#.#..#..#..##....#...#
+#......##.....##..##.##...#....
+#.....#.....#.#........#.......
+.#.....#.................#....#
+.###....#...#............#.#.#.
+.#...#.#......#.#..............
+....#...#......#.....#.......#.
+........#.....#..........#....#
+#..#......#...#...#.........#..
+#....#......#...##.#...#...#...
+#...#....#....#..#..#.....#..#.
+#......##..#..#.#.#..#.#.......
+..#..#...............#...##...#
+............#..............#.##
+.#.#.#......##.......#.......#.
+....#.........##.......#...###.
+.......#.#...#.#.#.......#.....
+....#..#..#...#....#.##.#.##...
+...##.##.#...#......#..........
+#.....#...#.#...#.##..##.#.....
+.......#.....#...#.#...##.#....
+.#.............#.....#....##..#
+##......#.......#...#....#.....
+.###......#.................#..
+#.#......##.........##..#......
+...#....#..........#.#.........
+..##..#.........#..............
+.....#...#..................#.#
+.............#.........#...#..#
+....#....#......#.#.......#...#
+#..#............#.#.......#...#
+..#.....#............#.........
+.#.....................###....#
+........#.####.........#.#.#...
+#...........##...#.........#..#
+...........#..#......#...#.#...
+....##...##.....#.....#........

2020/samples/03.txt

@@ -0,0 +1,11 @@
+..##.......
+#...#...#..
+.#....#..#.
+..#.#...#.#
+.#...##..#.
+..#.##.....
+.#.#.#....#
+.#........#
+#.##...#...
+#...##....#
+.#..#...#.#

2020/src/common.rs

@@ -34,6 +34,30 @@ where
     buf.trim().parse().unwrap()
 }
 
+pub fn read_char_grid(input: &mut dyn Read) -> Vec<Vec<u8>> {
+    let mut reader = BufReader::new(input);
+    let mut buffer = Vec::new();
+
+    let mut grid = Vec::new();
+
+    while let Ok(read) = reader.read_until(b'\n', &mut buffer) {
+        if read == 0 {
+            break;
+        }
+
+        let line: &[u8] = if let Some(&b'\n') = buffer.last() {
+            &buffer[..(buffer.len() - 1)]
+        } else {
+            &buffer[..]
+        };
+
+        grid.push(line.to_owned());
+        buffer.clear();
+    }
+
+    grid
+}
+
 /// An interface to count elements in particular categories.
 pub trait GroupingCount {
     /// The type of the categories under inspection

2020/src/day03.rs

@@ -0,0 +1,60 @@
+use std::io::Read;
+
+use crate::common::read_char_grid;
+use crate::Solution;
+
+#[derive(Default)]
+pub struct Day03;
+
+fn walk(right: usize, down: usize, forrest: &[Vec<u8>]) -> usize {
+    let mut trees = 0;
+    let mut x = 0;
+
+    for line in forrest.iter().step_by(down) {
+        if line[x] == b'#' {
+            trees += 1;
+        }
+
+        x = (x + right) % line.len();
+    }
+
+    trees
+}
+
+impl Solution for Day03 {
+    fn part1(&mut self, input: &mut dyn Read) -> String {
+        let forrest = read_char_grid(input);
+
+        walk(3, 1, &forrest).to_string()
+    }
+
+    fn part2(&mut self, input: &mut dyn Read) -> String {
+        let forrest = read_char_grid(input);
+        let mut product = 1;
+
+        for &(right, down) in &[(1, 1), (3, 1), (5, 1), (7, 1), (1, 2)] {
+            product *= walk(right, down, &forrest);
+        }
+
+        product.to_string()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::test_implementation;
+
+    use super::*;
+
+    const SAMPLE: &[u8] = include_bytes!("../samples/03.txt");
+
+    #[test]
+    fn sample_part1() {
+        test_implementation!(Day03, 1, SAMPLE, 7);
+    }
+
+    #[test]
+    fn sample_part2() {
+        test_implementation!(Day03, 2, SAMPLE, 336);
+    }
+}

2020/src/lib.rs

@@ -17,6 +17,7 @@ pub fn get_implementation(day: usize) -> Box<dyn Solution> {
     match day {
         1 => Box::new(day01::Day01::default()),
         2 => Box::new(day02::Day02::default()),
+        3 => Box::new(day03::Day03::default()),
         _ => panic!("Unsupported day {}", day),
     }
 }