day 18

5 files changed, 991 insertions, 0 deletions

diff --git a/benches/2023.rs b/benches/2023.rs
index b8b707b..0790c95 100644
--- a/benches/2023.rs
+++ b/benches/2023.rs
@@ -35,6 +35,8 @@ mod day15;
 mod day16;
 #[path = "../src/bin/2023/day17.rs"]
 mod day17;
+#[path = "../src/bin/2023/day18.rs"]
+mod day18;
 // NEXT MOD
 
 day!(2023, 1, day1);
@@ -54,6 +56,7 @@ day!(2023, 14, day14);
 day!(2023, 15, day15);
 day!(2023, 16, day16);
 day!(2023, 17, day17);
+day!(2023, 18, day18);
 // NEXT DAY
 
 fn bench_2023(c: &mut criterion::Criterion) {
@@ -76,6 +79,7 @@ fn bench_2023(c: &mut criterion::Criterion) {
             day_combined!(2023, 15, day15);
             day_combined!(2023, 16, day16);
             day_combined!(2023, 17, day17);
+            day_combined!(2023, 18, day18);
             // NEXT DAY COMBINED
         })
     });
@@ -101,5 +105,6 @@ criterion::criterion_main!(
     bench_2023day15,
     bench_2023day16,
     bench_2023day17,
+    bench_2023day18,
     // NEXT GROUP
 );
diff --git a/data/2023/18.txt b/data/2023/18.txt
new file mode 100644
index 0000000..a35bb5d
--- /dev/null
+++ b/data/2023/18.txt
@@ -0,0 +1,678 @@
+R 6 (#0e4c90)
+U 2 (#5b83a3)
+R 7 (#1a3a90)
+U 2 (#64e9b1)
+R 8 (#27d840)
+D 7 (#069321)
+R 3 (#08be10)
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+R 6 (#42e460)
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+R 5 (#281990)
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+L 7 (#376762)
+U 5 (#11c443)
+L 2 (#487de2)
+U 7 (#6e1383)
+L 7 (#184542)
+U 7 (#12f1d3)
diff --git a/src/bin/2023/day18.rs b/src/bin/2023/day18.rs
new file mode 100644
index 0000000..74e2611
--- /dev/null
+++ b/src/bin/2023/day18.rs
@@ -0,0 +1,232 @@
+#![allow(dead_code)]
+#![allow(unused_variables)]
+
+use advent_of_code::prelude::*;
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
+enum Direction {
+    Up,
+    Down,
+    Left,
+    Right,
+}
+
+impl Direction {
+    fn from_pos(row: Row, col: Col, new_row: Row, new_col: Col) -> Self {
+        if row.abs_diff(new_row) == Row(1) && col.abs_diff(new_col) == Col(0)
+        {
+            if row > new_row {
+                Self::Up
+            } else {
+                Self::Down
+            }
+        } else if col.abs_diff(new_col) == Col(1)
+            && row.abs_diff(new_row) == Row(0)
+        {
+            if col > new_col {
+                Self::Left
+            } else {
+                Self::Right
+            }
+        } else {
+            panic!("invalid direction ({row:?}, {col:?}) -> ({new_row:?}, {new_col:?})")
+        }
+    }
+
+    fn horizontal(&self) -> bool {
+        matches!(self, Self::Left | Self::Right)
+    }
+
+    fn increasing(&self) -> bool {
+        matches!(self, Self::Down | Self::Right)
+    }
+
+    fn turns(&self) -> [Self; 2] {
+        match self {
+            Self::Up | Self::Down => [Self::Left, Self::Right],
+            Self::Left | Self::Right => [Self::Up, Self::Down],
+        }
+    }
+
+    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 offset(&self) -> (IRow, ICol) {
+        match self {
+            Self::Up => (IRow(-1), ICol(0)),
+            Self::Down => (IRow(1), ICol(0)),
+            Self::Left => (IRow(0), ICol(-1)),
+            Self::Right => (IRow(0), ICol(1)),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct Instruction {
+    direction: Direction,
+    distance: isize,
+    real_direction: Direction,
+    real_distance: isize,
+}
+
+impl std::str::FromStr for Instruction {
+    type Err = anyhow::Error;
+
+    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
+        let cap = regex_captures!(
+            r"^(U|D|L|R) (\d+) \(#([0-9a-f]{5})([0-9a-f])\)",
+            s
+        )
+        .ok_or_else(|| anyhow::anyhow!("failed to parse line"))?;
+
+        let direction = match &cap[1] {
+            "U" => Direction::Up,
+            "D" => Direction::Down,
+            "L" => Direction::Left,
+            "R" => Direction::Right,
+            _ => bail!("unknown direction {}", &cap[1]),
+        };
+        let distance = cap[2].parse()?;
+        let real_direction = match &cap[4] {
+            "0" => Direction::Right,
+            "1" => Direction::Down,
+            "2" => Direction::Left,
+            "3" => Direction::Up,
+            _ => bail!("unknown real direction in {}", &cap[4]),
+        };
+        let real_distance = isize::from_str_radix(&cap[3], 16)?;
+
+        Ok(Self {
+            direction,
+            distance,
+            real_direction,
+            real_distance,
+        })
+    }
+}
+
+pub fn parse(fh: File) -> Result<Vec<Instruction>> {
+    Ok(parse::lines(fh).collect())
+}
+
+pub fn part1(instructions: Vec<Instruction>) -> Result<i64> {
+    let mut map: Grid<bool> = Grid::default();
+    let mut pos = (IRow(0), ICol(0));
+    let mut corners = vec![pos];
+    for instruction in &instructions {
+        let offset = instruction.direction.offset();
+        pos = (
+            pos.0 + offset.0 * instruction.distance,
+            pos.1 + offset.1 * instruction.distance,
+        );
+        corners.push(pos);
+    }
+    let min_row = corners.iter().map(|(row, _)| row).min().unwrap();
+    let min_col = corners.iter().map(|(_, col)| col).min().unwrap();
+
+    let starting_pos =
+        (Row(min_row.0.abs_diff(0)), Col(min_col.0.abs_diff(0)));
+    let mut pos = starting_pos;
+    for instruction in &instructions {
+        let offset = instruction.direction.offset();
+        for _ in 0..instruction.distance {
+            pos = (
+                Row(pos.0 .0.checked_add_signed(offset.0 .0).unwrap()),
+                Col(pos.1 .0.checked_add_signed(offset.1 .0).unwrap()),
+            );
+            map.grow(pos.0 + 1, pos.1 + 1);
+            map[pos.0][pos.1] = true;
+        }
+    }
+
+    let trench: HashSet<_> = map
+        .indexed_cells()
+        .filter_map(
+            |((row, col), dug)| if *dug { Some((row, col)) } else { None },
+        )
+        .collect();
+    let mut internal_cell = None;
+    for (row, col) in map.adjacent(starting_pos.0, starting_pos.1, true) {
+        if trench.contains(&(row, col)) {
+            continue;
+        }
+        let mut count = 0;
+        for offset in 0..=(row.0.min(col.0)) {
+            let check_row = row - offset;
+            let check_col = col - offset;
+            if trench.contains(&(check_row, check_col)) {
+                count += 1;
+            }
+        }
+        if count % 2 == 1 {
+            internal_cell = Some((row, col));
+        }
+    }
+    let internal_cell = internal_cell.unwrap();
+    map.flood_fill(internal_cell.0, internal_cell.1, &true, true);
+
+    Ok(map.cells().filter(|dug| **dug).count().try_into().unwrap())
+}
+
+pub fn part2(instructions: Vec<Instruction>) -> Result<i64> {
+    let mut pos = (IRow(0), ICol(0));
+
+    let mut vertices = vec![pos];
+    let mut last_left = false;
+    for pair in instructions.windows(2) {
+        let instruction = &pair[0];
+        let next_instruction = &pair[1];
+        let mut distance = instruction.real_distance + 1;
+        if last_left {
+            distance -= 1;
+        }
+        if instruction.real_direction.turn_left()
+            == next_instruction.real_direction
+        {
+            distance -= 1;
+            last_left = true;
+        } else {
+            last_left = false;
+        }
+        let offset = instruction.real_direction.offset();
+        pos = (pos.0 + offset.0 * distance, pos.1 + offset.1 * distance);
+        vertices.push(pos);
+    }
+
+    let mut area = 0;
+    for i in 0..vertices.len() {
+        let next = if i == vertices.len() - 1 { 0 } else { i + 1 };
+        area += vertices[i].0 .0 * vertices[next].1 .0
+            - vertices[next].0 .0 * vertices[i].1 .0;
+    }
+    area /= 2;
+
+    Ok(area.abs().try_into().unwrap())
+}
+
+#[test]
+fn test() {
+    assert_eq!(
+        part1(parse(parse::data(2023, 18).unwrap()).unwrap()).unwrap(),
+        36807
+    );
+    assert_eq!(
+        part2(parse(parse::data(2023, 18).unwrap()).unwrap()).unwrap(),
+        48797603984357
+    );
+}
diff --git a/src/bin/2023/main.rs b/src/bin/2023/main.rs
index 25f7c4d..b9eb819 100644
--- a/src/bin/2023/main.rs
+++ b/src/bin/2023/main.rs
@@ -28,6 +28,7 @@ mod day14;
 mod day15;
 mod day16;
 mod day17;
+mod day18;
 // NEXT MOD
 
 #[paw::main]
@@ -51,6 +52,7 @@ fn main(opt: Opt) -> Result<()> {
         15 => advent_of_code::day!(2023, opt.day, opt.puzzle, day15),
         16 => advent_of_code::day!(2023, opt.day, opt.puzzle, day16),
         17 => advent_of_code::day!(2023, opt.day, opt.puzzle, day17),
+        18 => advent_of_code::day!(2023, opt.day, opt.puzzle, day18),
         // NEXT PART
         _ => panic!("unknown day {}", opt.day),
     }
diff --git a/src/grid.rs b/src/grid.rs
index b006882..63fab03 100644
--- a/src/grid.rs
+++ b/src/grid.rs
@@ -34,6 +34,13 @@ impl std::ops::Add<Row> for usize {
     }
 }
 
+impl std::ops::Add<Row> for Row {
+    type Output = Row;
+    fn add(self, other: Row) -> Self::Output {
+        Row(self.0 + other.0)
+    }
+}
+
 impl std::ops::Add<usize> for Col {
     type Output = Self;
     fn add(self, other: usize) -> Self::Output {
@@ -48,6 +55,13 @@ impl std::ops::Add<Col> for usize {
     }
 }
 
+impl std::ops::Add<Col> for Col {
+    type Output = Col;
+    fn add(self, other: Col) -> Self::Output {
+        Col(self.0 + other.0)
+    }
+}
+
 impl std::ops::Sub<usize> for Row {
     type Output = Self;
     fn sub(self, other: usize) -> Self::Output {
@@ -168,6 +182,13 @@ impl std::ops::Add<IRow> for isize {
     }
 }
 
+impl std::ops::Add<IRow> for IRow {
+    type Output = IRow;
+    fn add(self, other: IRow) -> Self::Output {
+        IRow(self.0 + other.0)
+    }
+}
+
 impl std::ops::Add<isize> for ICol {
     type Output = Self;
     fn add(self, other: isize) -> Self::Output {
@@ -182,6 +203,13 @@ impl std::ops::Add<ICol> for isize {
     }
 }
 
+impl std::ops::Add<ICol> for ICol {
+    type Output = ICol;
+    fn add(self, other: ICol) -> Self::Output {
+        ICol(self.0 + other.0)
+    }
+}
+
 impl std::ops::Sub<isize> for IRow {
     type Output = Self;
     fn sub(self, other: isize) -> Self::Output {
@@ -210,6 +238,34 @@ impl std::ops::Sub<ICol> for isize {
     }
 }
 
+impl std::ops::Mul<isize> for IRow {
+    type Output = Self;
+    fn mul(self, other: isize) -> Self::Output {
+        Self(self.0 * other)
+    }
+}
+
+impl std::ops::Mul<IRow> for isize {
+    type Output = IRow;
+    fn mul(self, other: IRow) -> Self::Output {
+        IRow(self * other.0)
+    }
+}
+
+impl std::ops::Mul<isize> for ICol {
+    type Output = Self;
+    fn mul(self, other: isize) -> Self::Output {
+        Self(self.0 * other)
+    }
+}
+
+impl std::ops::Mul<ICol> for isize {
+    type Output = ICol;
+    fn mul(self, other: ICol) -> Self::Output {
+        ICol(self * other.0)
+    }
+}
+
 #[derive(Default, Clone, Debug, Eq, PartialEq, Hash)]
 pub struct GridRow<T: Clone + Eq + PartialEq + std::hash::Hash> {
     cells: Vec<T>,
@@ -330,6 +386,24 @@ impl<T: Clone + Eq + PartialEq + std::hash::Hash> Grid<T> {
             pos: 0,
         }
     }
+
+    pub fn flood_fill(
+        &mut self,
+        row: Row,
+        col: Col,
+        fill: &T,
+        diagonal: bool,
+    ) {
+        let mut todo = vec![(row, col)];
+        while let Some((row, col)) = todo.pop() {
+            self[row][col] = fill.clone();
+            for (row, col) in self.adjacent(row, col, diagonal) {
+                if self[row][col] != *fill {
+                    todo.push((row, col));
+                }
+            }
+        }
+    }
 }
 
 impl<T: Default + Clone + Eq + PartialEq + std::hash::Hash> Grid<T> {