Simple type to help clippy

2022/inputs/23.txt

@@ -0,0 +1,73 @@
+#.##.##...####..#.##.##....###....##...#..#####..#.##.##.#...###.##..#.##
+.#....#..#.##..#.#.#...#..#..####..#.#.##.#.#..#.#..#.#..##.#..........#.
+##.#####.###.#...######..###.#.#..##.#.##.#......#..##.....###.#.##.##.##
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+.#####..###.#.###.###....#..#..#....#.##.#.###.#.####..###.#####.#.#####.
+...#..##.##.#.#.###.#######.##.#...##..##...#......#..####.#.#...#.#####.
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+......#.###.#.##..####..#..##..##.###.#..##...#...#...#...#.###.#.#.##.##
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+.#.##...#...###..#..#.#.#..#.#.#.#.##........#.##.#.#.##.##.#.#.##.######
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+####.##..........###.###.#####.#.#..##...##.....#..###..##..#.####..#.##.
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+#.#######..#.##.#.#.#..####..##.#..###.####.#..#########....####....###..
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+.#..##.#.##..#......##.#.#.##.#####.#.###....#...###...#....#.###.....###
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+.##..###.####.#..#####.###..###..#......##...#.....####..###..#..##.#.##.
+......###.#..#...#..#.#.##.#.###...##.#.#....####.#..#.######.#.#...####.
+...#.##.####....##..##.#.###.###.....#..###...####..##..######.#..##.....
+.....####.....###.#.#.......#####.#.#....##...#####..#..#.#..#.#.#..##.##
+##..##.#..##..#..#.#####..##.####.#...#.#..#..###..#..#....#...#.###.##..
+#.#..#.#########.####..#####..####.#.#####....#.#..##...#..####.#..###.#.
+#..##.###.##..#....#...#..#.##..#..###..#####..#######.#####....#.##.....
+####.####.########.#.###....#.#..#..#.#.#.#..#....#..#.....#..##..#.##.#.

2022/src/day22.rs

@@ -1,9 +1,190 @@
+use anyhow::Context;
 use anyhow::Result;
+use nom::branch::alt;
+use nom::bytes::complete::tag;
+use nom::bytes::complete::take_until;
+use nom::character::complete::newline;
+use nom::combinator::map;
+use nom::combinator::value;
+use nom::multi::many1;
+use nom::sequence::separated_pair;
+use nom::sequence::terminated;
+use nom::IResult;
 
-pub fn part1(_input: &[u8]) -> Result<String> {
-    anyhow::bail!("not implemented")
+use crate::common::parse_input;
+
+#[derive(Clone, Copy, Debug)]
+enum Step {
+    Forward(u32),
+    Left,
+    Right,
+}
+
+#[derive(Clone, Copy)]
+enum Direction {
+    Up = 3,
+    Down = 1,
+    Left = 2,
+    Right = 0,
+}
+
+type Map<'a> = Vec<&'a [u8]>;
+
+impl Direction {
+    fn turn_left(self) -> Self {
+        match self {
+            Direction::Up => Direction::Left,
+            Direction::Down => Direction::Right,
+            Direction::Left => Direction::Down,
+            Direction::Right => Direction::Up,
+        }
+    }
+
+    fn turn_right(self) -> Self {
+        match self {
+            Direction::Up => Direction::Right,
+            Direction::Down => Direction::Left,
+            Direction::Left => Direction::Up,
+            Direction::Right => Direction::Down,
+        }
+    }
+}
+
+fn parse_map(input: &[u8]) -> IResult<&[u8], (Map, Vec<Step>)> {
+    separated_pair(
+        map(take_until("\n\n"), |map: &[u8]| {
+            map.split(|&b| b == b'\n').collect()
+        }),
+        tag("\n\n"),
+        terminated(
+            many1(alt((
+                map(nom::character::complete::u32, Step::Forward),
+                value(Step::Right, tag("R")),
+                value(Step::Left, tag("L")),
+            ))),
+            newline,
+        ),
+    )(input)
+}
+
+pub fn part1(input: &[u8]) -> Result<String> {
+    let (map, steps) = parse_input(input, parse_map)?;
+    let mut dir = Direction::Right;
+    let mut y = 0;
+    let mut x = map[y]
+        .iter()
+        .position(|&b| b == b'.')
+        .context("Could not find starting position")?;
+
+    for step in steps {
+        match step {
+            Step::Forward(amount) => match dir {
+                Direction::Up => {
+                    for _ in 0..amount {
+                        if y == 0 || map[y - 1].get(x).map(|&b| b == b' ').unwrap_or(true) {
+                            let new_y = map
+                                .iter()
+                                .rposition(|line| {
+                                    line.get(x)
+                                        .map(|&b| b == b'.' || b == b'#')
+                                        .unwrap_or(false)
+                                })
+                                .unwrap();
+                            if map[new_y][x] == b'#' {
+                                break;
+                            } else {
+                                y = new_y;
+                            }
+                        } else if map[y - 1][x] == b'#' {
+                            break;
+                        } else {
+                            y -= 1;
+                        }
+                    }
+                }
+                Direction::Down => {
+                    for _ in 0..amount {
+                        if y + 1 >= map.len()
+                            || map[y + 1].get(x).map(|&b| b == b' ').unwrap_or(true)
+                        {
+                            let new_y = map
+                                .iter()
+                                .position(|line| {
+                                    line.get(x)
+                                        .map(|&b| b == b'.' || b == b'#')
+                                        .unwrap_or(false)
+                                })
+                                .unwrap();
+
+                            if map[new_y][x] == b'#' {
+                                break;
+                            } else {
+                                y = new_y;
+                            }
+                        } else if map[y + 1][x] == b'#' {
+                            break;
+                        } else {
+                            y += 1;
+                        }
+                    }
+                }
+                Direction::Left => {
+                    for _ in 0..amount {
+                        if x == 0 || map[y][x - 1] == b' ' {
+                            let new_x = map[y]
+                                .iter()
+                                .rposition(|&b| b == b'.' || b == b'#')
+                                .unwrap();
+                            if map[y][new_x] == b'.' {
+                                x = new_x;
+                            } else {
+                                break;
+                            }
+                        } else if map[y][x - 1] == b'#' {
+                            break;
+                        } else {
+                            x -= 1;
+                        }
+                    }
+                }
+                Direction::Right => {
+                    for _ in 0..amount {
+                        if x + 1 >= map[y].len() || map[y][x + 1] == b' ' {
+                            let new_x =
+                                map[y].iter().position(|&b| b == b'.' || b == b'#').unwrap();
+                            if map[y][new_x] == b'.' {
+                                x = new_x;
+                            } else {
+                                break;
+                            }
+                        } else if map[y][x + 1] == b'#' {
+                            break;
+                        } else {
+                            x += 1;
+                        }
+                    }
+                }
+            },
+            Step::Left => dir = dir.turn_left(),
+            Step::Right => dir = dir.turn_right(),
+        }
+    }
+
+    Ok((1000 * (y + 1) + 4 * (x + 1) + dir as usize).to_string())
 }
 
 pub fn part2(_input: &[u8]) -> Result<String> {
     anyhow::bail!("not implemented")
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const SAMPLE: &[u8] = include_bytes!("samples/22.txt");
+
+    #[test]
+    fn sample_part1() {
+        assert_eq!(part1(SAMPLE).unwrap(), "6032");
+    }
+}

2022/src/day23.rs

@@ -1,9 +1,205 @@
+use std::collections::hash_map::Entry;
+use std::ops::RangeInclusive;
+
+use ahash::AHashMap;
+use ahash::AHashSet;
+use anyhow::Context;
 use anyhow::Result;
+use itertools::Itertools;
+use nom::bytes::complete::take_until;
+use nom::character::complete::newline;
+use nom::multi::fold_many1;
+use nom::sequence::terminated;
+use nom::IResult;
 
-pub fn part1(_input: &[u8]) -> Result<String> {
-    anyhow::bail!("not implemented")
+use crate::common::enumerate;
+use crate::common::parse_input;
+use crate::common::Vec2;
+
+const OPTIONS: [[Vec2; 3]; 4] = [
+    // North
+    [Vec2([0, -1]), Vec2([-1, -1]), Vec2([1, -1])],
+    // South
+    [Vec2([0, 1]), Vec2([-1, 1]), Vec2([1, 1])],
+    // West
+    [Vec2([-1, 0]), Vec2([-1, -1]), Vec2([-1, 1])],
+    // East
+    [Vec2([1, 0]), Vec2([1, -1]), Vec2([1, 1])],
+];
+
+fn parse_elves(input: &[u8]) -> IResult<&[u8], AHashSet<Vec2>> {
+    fold_many1(
+        enumerate(terminated(take_until("\n"), newline)),
+        AHashSet::new,
+        |mut elves, (y, line): (usize, &[u8])| {
+            let y = y as i32;
+
+            elves.extend(
+                line.iter()
+                    .enumerate()
+                    .filter_map(|(x, &val)| (val == b'#').then_some(Vec2([x as i32, y]))),
+            );
+
+            elves
+        },
+    )(input)
 }
 
-pub fn part2(_input: &[u8]) -> Result<String> {
-    anyhow::bail!("not implemented")
+fn determine_bounding_box(
+    elves: &AHashSet<Vec2>,
+) -> Result<(RangeInclusive<i32>, RangeInclusive<i32>)> {
+    let (x_min, x_max) = elves
+        .iter()
+        .map(|&Vec2([x, _])| x)
+        .minmax()
+        .into_option()
+        .context("Could not determine x range")?;
+
+    let (y_min, y_max) = elves
+        .iter()
+        .map(|&Vec2([_, y])| y)
+        .minmax()
+        .into_option()
+        .context("Could not determine y range")?;
+
+    Ok((x_min..=x_max, y_min..=y_max))
+}
+
+#[allow(unused)]
+fn print(elves: &AHashSet<Vec2>) -> Result<()> {
+    let (x_bounds, y_bounds) = determine_bounding_box(elves)?;
+
+    for y in y_bounds {
+        for x in x_bounds.clone() {
+            print!(
+                "{}",
+                if elves.contains(&Vec2([x, y])) {
+                    '#'
+                } else {
+                    '.'
+                }
+            );
+        }
+
+        println!();
+    }
+
+    Ok(())
+}
+
+pub fn part1(input: &[u8]) -> Result<String> {
+    let mut elves = parse_input(input, parse_elves)?;
+
+    simulate(&mut elves, 10);
+
+    let (x_bounds, y_bounds) = determine_bounding_box(&elves)?;
+
+    let area = (x_bounds.end() - x_bounds.start() + 1) * (y_bounds.end() - y_bounds.start() + 1);
+
+    let free = area - elves.len() as i32;
+
+    Ok(free.to_string())
+}
+
+fn simulate(elves: &mut AHashSet<Vec2>, max: usize) -> Option<usize> {
+    let mut todo = Vec::new();
+    let mut to_return = Vec::new();
+    let mut origin = AHashMap::new();
+
+    for it in 0..max {
+        // Remove all todos from a previous iteration
+        todo.clear();
+
+        // Find all the elves with at least one neighbour
+        todo.extend(elves.iter().copied().filter(|&Vec2([x, y])| {
+            for dx in [-1, 0, 1] {
+                for dy in [-1, 0, 1] {
+                    if dx == 0 && dy == 0 {
+                        continue;
+                    }
+
+                    if elves.contains(&Vec2([x + dx, y + dy])) {
+                        return true;
+                    }
+                }
+            }
+
+            false
+        }));
+
+        for &elf in &todo {
+            let mut moved = false;
+
+            for &deltas in OPTIONS[(it % 4)..].iter().chain(&OPTIONS[..(it % 4)]) {
+                if deltas
+                    .into_iter()
+                    .all(|delta| !elves.contains(&(elf + delta)))
+                {
+                    // Observation: any collision will only happen between opposite pairs of elves,
+                    // not three. Otherwise they wouldn't have chosen to move this direction.
+
+                    // Somewhat messy but it avoids computing the hash more than once per elf
+                    match origin.entry(deltas[0] + elf) {
+                        Entry::Occupied(entry) => {
+                            to_return.push(elf);
+                            to_return.push(entry.remove());
+                        }
+                        Entry::Vacant(entry) => {
+                            entry.insert(elf);
+                        }
+                    };
+
+                    // We moved, or collided, but we shouldn't look other directions any more
+                    moved = true;
+                    break;
+                }
+            }
+
+            if !moved {
+                to_return.push(elf);
+            }
+        }
+
+        if origin.is_empty() {
+            return Some(it + 1);
+        }
+
+        // Remove entries we processed
+        for elf in &todo {
+            elves.remove(elf);
+        }
+
+        // Add back any entries we ended up not moving
+        elves.extend(to_return.drain(..));
+
+        // Add all the elves in their new positions
+        elves.extend(origin.drain().map(|(dest, _)| dest));
+    }
+
+    None
+}
+
+pub fn part2(input: &[u8]) -> Result<String> {
+    let mut elves = parse_input(input, parse_elves)?;
+
+    let first_non_moved = simulate(&mut elves, usize::MAX).context("Elves didn't stop moving?")?;
+
+    Ok(first_non_moved.to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const SAMPLE: &[u8] = include_bytes!("./samples/23.txt");
+
+    #[test]
+    fn sample_part1() {
+        assert_eq!(part1(SAMPLE).unwrap(), "110");
+    }
+
+    #[test]
+    fn sample_part2() {
+        assert_eq!(part2(SAMPLE).unwrap(), "20");
+    }
 }

2022/src/samples/22.txt

@@ -0,0 +1,14 @@
+        ...#
+        .#..
+        #...
+        ....
+...#.......#
+........#...
+..#....#....
+..........#.
+        ...#....
+        .....#..
+        .#......
+        ......#.
+
+10R5L5R10L4R5L5

2022/src/samples/23.txt

@@ -0,0 +1,12 @@
+..............
+..............
+.......#......
+.....###.#....
+...#...#.#....
+....#...##....
+...#.###......
+...##.#.##....
+....#..#......
+..............
+..............
+..............