day(17): add solution

Signed-off-by: Matej Focko <me@mfocko.xyz>

samples/day17.txt

@@ -0,0 +1 @@
+>>><<><>><<<>><>>><<<>>><<<><<<>><>><<>>

src/bin/day17.rs

@@ -0,0 +1,206 @@
+use std::collections::HashMap;
+
+use aoc_2022::*;
+
+type Input = Vec<char>;
+type Output = usize;
+
+type Position = Vector2D<isize>;
+
+struct InfiniteIndex {
+    size: usize,
+    i: usize,
+}
+
+impl InfiniteIndex {
+    fn new(size: usize) -> InfiniteIndex {
+        InfiniteIndex { size, i: size - 1 }
+    }
+}
+
+impl Iterator for InfiniteIndex {
+    type Item = usize;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.i = (self.i + 1) % self.size;
+        Some(self.i)
+    }
+}
+
+struct Tunnel {
+    buffer: usize,
+    jets: Vec<char>,
+    rocks: Vec<Vec<char>>,
+    flushed: usize,
+    next_jet: InfiniteIndex,
+    next_shape: InfiniteIndex,
+}
+
+lazy_static! {
+    static ref SHAPES: Vec<Vec<Vec<char>>> = vec![
+        vec!["####"],
+        vec![" # ", "###", " # "],
+        vec!["  #", "  #", "###"],
+        vec!["#", "#", "#", "#"],
+        vec!["##", "##"],
+    ]
+    .iter()
+    .map(|shape| shape.iter().map(|l| l.chars().collect()).collect())
+    .collect_vec();
+}
+
+fn below(position: Vector2D<isize>) -> Vector2D<isize> {
+    position + Vector2D::new(0, 1)
+}
+
+fn left(position: Vector2D<isize>) -> Vector2D<isize> {
+    position + Vector2D::new(-1, 0)
+}
+
+fn right(position: Vector2D<isize>) -> Vector2D<isize> {
+    position + Vector2D::new(1, 0)
+}
+
+fn occupied(shape: &[Vec<char>]) -> impl Iterator<Item = Position> + '_ {
+    shape.iter().enumerate().flat_map(|(y, row)| {
+        row.iter().enumerate().filter_map(move |(x, c)| {
+            if c == &'#' {
+                Some(Vector2D::new(x as isize, y as isize))
+            } else {
+                None
+            }
+        })
+    })
+}
+
+impl Tunnel {
+    fn new(buffer: usize, jets: Vec<char>) -> Tunnel {
+        let jet_count = jets.len();
+
+        Tunnel {
+            buffer,
+            jets,
+            rocks: vec!["#########".chars().collect_vec()],
+            flushed: 0,
+            next_jet: InfiniteIndex::new(jet_count),
+            next_shape: InfiniteIndex::new(SHAPES.len()),
+        }
+    }
+
+    fn hit(&self, shape: &[Vec<char>], position: Position) -> bool {
+        occupied(shape).any(|rock| self.rocks[position + rock] != ' ')
+    }
+
+    fn emplace(&mut self, shape: &[Vec<char>], position: Position) {
+        for rock in occupied(shape) {
+            self.rocks[position + rock] = '#';
+        }
+
+        while !self.rocks.first().unwrap().contains(&'#') {
+            self.rocks.remove(0);
+        }
+
+        while self.rocks.len() > self.buffer {
+            self.rocks.pop();
+            self.flushed += 1;
+        }
+    }
+
+    fn add_one(&mut self) {
+        let shape = &SHAPES[self.next_shape.next().unwrap()];
+
+        for _ in 0..shape.len() + 3 {
+            self.rocks.insert(0, "|       |".chars().collect_vec());
+        }
+
+        let mut position = Vector2D::new(3, 0);
+        loop {
+            let jet = self.jets[self.next_jet.next().unwrap()];
+
+            if jet == '>' && !self.hit(shape, right(position)) {
+                position = right(position);
+            } else if jet == '<' && !self.hit(shape, left(position)) {
+                position = left(position);
+            }
+
+            if self.hit(shape, below(position)) {
+                break;
+            }
+
+            position = below(position);
+        }
+
+        self.emplace(shape, position);
+    }
+
+    fn add(&mut self, mut count: usize) -> &Tunnel {
+        let mut seen: HashMap<String, (usize, usize)> = HashMap::new();
+
+        while count > 0 {
+            let hash = self.rocks.iter().map(|l| l.iter().join("")).join("");
+
+            match seen.get(&hash) {
+                Some((to_add, height)) => {
+                    let p_height = self.height() - height;
+                    let p_length = to_add - count;
+
+                    self.flushed += (count / p_length) * p_height;
+                    count %= p_length;
+                    break;
+                }
+                None => {
+                    seen.insert(hash, (count, self.height()));
+                    self.add_one();
+                    count -= 1;
+                }
+            }
+        }
+
+        for _ in 0..count {
+            self.add_one();
+        }
+
+        self
+    }
+
+    fn height(&self) -> usize {
+        self.rocks.len() + self.flushed - 1
+    }
+}
+
+struct Day17;
+impl Solution<Input, Output> for Day17 {
+    fn parse_input<P: AsRef<Path>>(pathname: P) -> Input {
+        file_to_string(pathname).trim_end().chars().collect()
+    }
+
+    fn part_1(input: &Input) -> Output {
+        Tunnel::new(100, input.clone()).add(2022).height()
+    }
+
+    fn part_2(input: &Input) -> Output {
+        Tunnel::new(100, input.clone()).add(1000000000000).height()
+    }
+}
+
+fn main() -> Result<()> {
+    // Day17::run("sample")
+    Day17::main()
+}
+
+test_sample!(day_17, Day17, 3068, 1514285714288);
+
+#[cfg(test)]
+mod day_17_extended {
+    use super::*;
+
+    #[test]
+    fn test_infinite_index() {
+        let index = InfiniteIndex::new(3);
+
+        assert_eq!(
+            index.take(10).collect::<Vec<usize>>(),
+            vec![0, 1, 2, 0, 1, 2, 0, 1, 2, 0]
+        );
+    }
+}