day(22): finish it off…

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

src/bin/day22.rs

@@ -5,11 +5,28 @@ use aoc_2022::*;
 type Input = MonkeyMap;
 type Output = isize;
 
-type Position = Vector2D<usize>;
+type Position = Vector2D<isize>;
 type Direction = Vector2D<isize>;
 
+lazy_static! {
+    static ref DIRECTIONS: HashMap<Direction, usize> = HashMap::from([
+        (Direction::new(1, 0), 0),
+        (Direction::new(0, 1), 1),
+        (Direction::new(-1, 0), 2),
+        (Direction::new(0, -1), 3)
+    ]);
+}
+
+fn turn_left(d: Direction) -> Direction {
+    Direction::new(d.y(), -d.x())
+}
+
+fn turn_right(d: Direction) -> Direction {
+    Direction::new(-d.y(), d.x())
+}
+
 enum Instruction {
-    Move(usize),
+    Move(isize),
     TurnLeft,
     TurnRight,
 }
@@ -19,143 +36,238 @@ enum Orientation {
     Horizontal(usize),
     Vertical(usize),
 }
+impl Orientation {
+    fn horizontal(width: usize) -> Self {
+        Self::Horizontal(width)
+    }
+    fn vertical(height: usize) -> Self {
+        Self::Vertical(height)
+    }
+}
 
 struct MonkeyMap {
     map: Vec<Vec<char>>,
-    boundaries: HashMap<Orientation, Range<usize>>,
+    boundaries: HashMap<Orientation, Range<isize>>,
     instructions: Vec<Instruction>,
 }
 
-fn wrapping_step(position: usize, diff: isize, range: &Range<usize>) -> usize {
+fn wrapping_step(position: isize, diff: isize, range: &Range<isize>) -> isize {
     let (lower, upper) = (range.start, range.end);
-    let range_size = (upper - lower) as isize;
+    let range_size = upper - lower;
 
-    (lower as isize + (position as isize + diff - lower as isize + range_size) % range_size)
-        as usize
+    lower + (position + diff - lower + range_size) % range_size
 }
 
-trait Wrap {
-    fn next(&self, state: &State<'_>) -> (Position, Direction);
+trait Wrap: Clone {
+    type State;
+
+    // simulation
+    fn is_blocked(&self) -> bool;
+    fn step(&mut self, steps: isize);
+    fn turn_left(&mut self);
+    fn turn_right(&mut self);
+
+    // movement
+    fn next(&self) -> (Self::State, Direction);
+
+    // final answer
+    fn answer(&self) -> Output;
 }
 
-struct Wrap2D;
-impl Wrap for Wrap2D {
-    fn next(&self, state: &State<'_>) -> (Position, Direction) {
-        let h_bound = &state.input.boundaries[&Orientation::Horizontal(state.position.y())];
-        let v_bound = &state.input.boundaries[&Orientation::Vertical(state.position.x())];
-
-        (
-            Position::new(
-                wrapping_step(state.position.x(), state.direction.x(), h_bound),
-                wrapping_step(state.position.y(), state.direction.y(), v_bound),
-            ),
-            state.direction,
-        )
-    }
-}
-
-struct Face {
-    horizontal_bound: Range<usize>,
-    vertical_bound: Range<usize>,
-}
-
-struct Wrap3D {
-    faces: Vec<Face>,
-}
-impl Wrap3D {
-    fn face(&self, position: Position) -> &Face {
-        let (x, y) = (position.x(), position.y());
-
-        for f in &self.faces {}
-        todo!()
-    }
-}
-impl Wrap for Wrap3D {
-    fn next(&self, state: &State<'_>) -> (Position, Direction) {
-        let face = self.face(state.position);
-
-        (
-            Position::new(
-                wrapping_step(
-                    state.position.x(),
-                    state.direction.x(),
-                    &face.horizontal_bound,
-                ),
-                wrapping_step(
-                    state.position.y(),
-                    state.direction.y(),
-                    &face.vertical_bound,
-                ),
-            ),
-            state.direction,
-        )
-    }
-}
-
-struct State<'a> {
+#[derive(Clone, Copy)]
+struct Wrap2D<'a> {
     input: &'a Input,
     position: Position,
     direction: Direction,
 }
-
-impl<'a> State<'a> {
-    fn new(input: &'a Input) -> State<'a> {
+impl<'a> Wrap2D<'a> {
+    fn new(input: &'a Input) -> Wrap2D<'a> {
         Self {
             input,
             position: Position::new(input.boundaries[&Orientation::Horizontal(0)].start, 0),
             direction: Direction::new(1, 0),
         }
     }
+}
+impl Wrap for Wrap2D<'_> {
+    type State = Position;
 
-    fn is_blocked(&self, wrapper: &impl Wrap) -> bool {
-        let (next_position, _) = wrapper.next(self);
+    // simulation
+    fn is_blocked(&self) -> bool {
+        let (next_position, _) = self.next();
         self.input.map[next_position] == '#'
     }
 
-    fn step(&mut self, wrapper: &impl Wrap, steps: usize) {
+    fn step(&mut self, steps: isize) {
         for _ in 0..steps {
-            if self.is_blocked(wrapper) {
+            if self.is_blocked() {
                 return;
             }
-            (self.position, self.direction) = wrapper.next(self);
+            (self.position, self.direction) = self.next();
         }
     }
 
     fn turn_left(&mut self) {
-        let previous = self.direction;
-        self.direction = Direction::new(previous.y(), -previous.x());
+        self.direction = turn_left(self.direction);
     }
 
     fn turn_right(&mut self) {
-        let previous = self.direction;
-        self.direction = Direction::new(-previous.y(), previous.x());
+        self.direction = turn_right(self.direction);
+    }
+
+    // movement
+    fn next(&self) -> (Self::State, Direction) {
+        let h_bound = &self.input.boundaries[&Orientation::Horizontal(self.position.y() as usize)];
+        let v_bound = &self.input.boundaries[&Orientation::Vertical(self.position.x() as usize)];
+
+        (
+            Position::new(
+                wrapping_step(self.position.x(), self.direction.x(), h_bound),
+                wrapping_step(self.position.y(), self.direction.y(), v_bound),
+            ),
+            self.direction,
+        )
+    }
+
+    // final answer
+    fn answer(&self) -> Output {
+        1000 * (self.position.y() + 1)
+            + 4 * (self.position.x() + 1)
+            + DIRECTIONS[&self.direction] as isize
     }
 }
 
-lazy_static! {
-    static ref DIRECTIONS: HashMap<(isize, isize), usize> =
-        HashMap::from([((1, 0), 0), ((0, 1), 1), ((-1, 0), 2), ((0, -1), 3)]);
+#[derive(Clone)]
+struct Face {
+    horizontal_bound: Range<isize>,
+    vertical_bound: Range<isize>,
+    continuation: Vec<(usize, usize)>,
+}
+impl Face {
+    fn normalized(&self, p: Position) -> Position {
+        Position::new(
+            p.x() + self.horizontal_bound.start,
+            p.y() + self.vertical_bound.start,
+        )
+    }
 }
 
-fn solve(wrapper: &impl Wrap, input: &Input) -> Output {
-    let final_state = input
+#[derive(Debug, Clone)]
+struct State3D {
+    face: usize,
+    position: Position,
+}
+impl State3D {
+    fn global_position(&self, faces: &[Face]) -> Position {
+        faces[self.face].normalized(self.position)
+    }
+}
+
+#[derive(Clone)]
+struct Wrap3D<'a> {
+    input: &'a Input,
+    state: State3D,
+    direction: Direction,
+    faces: Vec<Face>,
+}
+impl<'a> Wrap3D<'a> {
+    fn new(configuration: Vec<Face>, input: &'a Input) -> Wrap3D<'a> {
+        Self {
+            input,
+            state: State3D {
+                face: 0,
+                position: Position::new(0, 0),
+            },
+            direction: Direction::new(1, 0),
+            faces: configuration,
+        }
+    }
+
+    fn face(&self) -> &Face {
+        &self.faces[self.state.face]
+    }
+}
+impl Wrap for Wrap3D<'_> {
+    type State = State3D;
+
+    // simulation
+    fn is_blocked(&self) -> bool {
+        let (next_state, _) = self.next();
+        self.input.map[next_state.global_position(&self.faces)] == '#'
+    }
+
+    fn step(&mut self, steps: isize) {
+        for _ in 0..steps {
+            if self.is_blocked() {
+                return;
+            }
+            (self.state, self.direction) = self.next();
+        }
+    }
+
+    fn turn_left(&mut self) {
+        self.direction = turn_left(self.direction);
+    }
+
+    fn turn_right(&mut self) {
+        self.direction = turn_right(self.direction);
+    }
+
+    // movement
+    fn next(&self) -> (Self::State, Direction) {
+        let side = self.faces[0].horizontal_bound.len() as isize;
+        let wraps =
+            |pos: Position| pos.x() < 0 || pos.x() >= side || pos.y() < 0 || pos.y() >= side;
+
+        let mut next_face = self.state.face;
+        let mut position = self.state.position + self.direction;
+        let mut direction = self.direction;
+
+        if wraps(position) {
+            let (face, rotations) = self.face().continuation[DIRECTIONS[&self.direction]];
+
+            next_face = face;
+            position = Position::new((position.x() + side) % side, (position.y() + side) % side);
+
+            for _ in 0..rotations {
+                position = Position::new(side - position.y() - 1, position.x());
+                direction = turn_right(direction)
+            }
+        }
+
+        (
+            State3D {
+                face: next_face,
+                position,
+            },
+            direction,
+        )
+    }
+
+    // final answer
+    fn answer(&self) -> Output {
+        1000 * (self.state.global_position(&self.faces).y() + 1)
+            + 4 * (self.state.global_position(&self.faces).x() + 1)
+            + DIRECTIONS[&self.direction] as isize
+    }
+}
+
+fn solve(initial_state: impl Wrap, input: &Input) -> Output {
+    input
         .instructions
         .iter()
-        .fold(State::new(input), |mut state, y| {
+        .fold(initial_state, |previous_state, y| {
+            let mut state = previous_state;
+
             match &y {
-                Instruction::Move(steps) => state.step(wrapper, *steps),
+                Instruction::Move(steps) => state.step(*steps),
                 Instruction::TurnLeft => state.turn_left(),
                 Instruction::TurnRight => state.turn_right(),
             }
 
             state
-        });
-
-    (1000 * (final_state.position.y() + 1)
-        + 4 * (final_state.position.x() + 1)
-        + DIRECTIONS[&(final_state.direction.x(), final_state.direction.y())])
-        .try_into()
-        .unwrap()
+        })
+        .answer()
 }
 
 struct Day22;
@@ -169,27 +281,39 @@ impl Solution<Input, Output> for Day22 {
         map.iter_mut().for_each(|l| l.resize(max_row_length, ' '));
 
         let mut boundaries = HashMap::new();
-        for row in 0..map.len() {
-            let mut first_non_empty = map[row].iter().enumerate().skip_while(|&(_, &c)| c == ' ');
-            let start = first_non_empty.next().unwrap().0;
+        let mut find_boundaries = |constructor: fn(usize) -> Orientation,
+                                   iterator: &mut dyn Iterator<Item = &char>,
+                                   upper_bound,
+                                   i| {
+            let mut first_non_empty = iterator.enumerate().skip_while(|&(_, &c)| c == ' ');
+            let start = first_non_empty.next().unwrap().0 as isize;
 
             let mut last_non_empty = first_non_empty.skip_while(|&(_, &c)| c != ' ');
-            let end = last_non_empty.next().unwrap_or((map[row].len(), &'_')).0;
+            let end = last_non_empty.next().unwrap_or((upper_bound, &'_')).0 as isize;
 
-            boundaries.insert(Orientation::Horizontal(row), start..end);
-        }
+            boundaries.insert(constructor(i), start..end);
+            (constructor(i), start..end)
+        };
 
-        for col in 0..map[0].len() {
-            let mut first_non_empty = ColumnIterator::new(&map, col)
-                .enumerate()
-                .skip_while(|&(_, &c)| c == ' ');
-            let start = first_non_empty.next().unwrap().0;
+        // construct all horizontal boundaries
+        (0..map.len()).for_each(|row| {
+            find_boundaries(
+                Orientation::horizontal,
+                &mut map[row].iter(),
+                map[row].len(),
+                row,
+            );
+        });
 
-            let mut last_non_empty = first_non_empty.skip_while(|&(_, &c)| c != ' ');
-            let end = last_non_empty.next().unwrap_or((map.len(), &'_')).0;
-
-            boundaries.insert(Orientation::Vertical(col), start..end);
-        }
+        // construct all vertical boundaries
+        (0..map[0].len()).for_each(|col| {
+            find_boundaries(
+                Orientation::vertical,
+                &mut ColumnIterator::new(&map, col),
+                map.len(),
+                col,
+            );
+        });
 
         let unparsed_instructions_str = instructions.trim_end();
 
@@ -204,7 +328,7 @@ impl Solution<Input, Output> for Day22 {
                 .collect();
             if !steps.is_empty() {
                 // found a move instruction
-                instructions.push(Instruction::Move(steps.parse::<usize>().unwrap()));
+                instructions.push(Instruction::Move(steps.parse::<isize>().unwrap()));
                 skip += steps.len();
                 continue;
             }
@@ -225,12 +349,79 @@ impl Solution<Input, Output> for Day22 {
     }
 
     fn part_1(input: &Input) -> Output {
-        solve(&Wrap2D, input)
+        solve(Wrap2D::new(input), input)
     }
 
     fn part_2(input: &Input) -> Output {
-        let wrapper = Wrap2D;
-        solve(&wrapper, input)
+        // sample
+        let config = vec![
+            Face {
+                horizontal_bound: 8..12,
+                vertical_bound: 0..4,
+                continuation: vec![(5, 2), (3, 0), (2, 1), (1, 2)],
+            },
+            Face {
+                horizontal_bound: 0..4,
+                vertical_bound: 4..8,
+                continuation: vec![(2, 0), (4, 2), (5, 3), (0, 2)],
+            },
+            Face {
+                horizontal_bound: 4..8,
+                vertical_bound: 4..8,
+                continuation: vec![(3, 0), (4, 3), (1, 0), (0, 1)],
+            },
+            Face {
+                horizontal_bound: 8..12,
+                vertical_bound: 4..8,
+                continuation: vec![(5, 1), (4, 0), (2, 0), (0, 0)],
+            },
+            Face {
+                horizontal_bound: 8..12,
+                vertical_bound: 8..12,
+                continuation: vec![(5, 0), (1, 2), (2, 1), (3, 0)],
+            },
+            Face {
+                horizontal_bound: 12..16,
+                vertical_bound: 8..12,
+                continuation: vec![(0, 2), (1, 2), (4, 0), (3, 3)],
+            },
+        ];
+
+        // challenge input
+        // let config = vec![
+        //     Face {
+        //         horizontal_bound: 50..100,
+        //         vertical_bound: 0..50,
+        //         continuation: vec![(1, 0), (2, 0), (3, 2), (5, 1)],
+        //     },
+        //     Face {
+        //         horizontal_bound: 100..150,
+        //         vertical_bound: 0..50,
+        //         continuation: vec![(4, 2), (2, 1), (0, 0), (5, 0)],
+        //     },
+        //     Face {
+        //         horizontal_bound: 50..100,
+        //         vertical_bound: 50..100,
+        //         continuation: vec![(1, 3), (4, 0), (3, 3), (0, 0)],
+        //     },
+        //     Face {
+        //         horizontal_bound: 0..50,
+        //         vertical_bound: 100..150,
+        //         continuation: vec![(4, 0), (5, 0), (0, 2), (2, 1)],
+        //     },
+        //     Face {
+        //         horizontal_bound: 50..100,
+        //         vertical_bound: 100..150,
+        //         continuation: vec![(1, 2), (5, 1), (3, 0), (2, 0)],
+        //     },
+        //     Face {
+        //         horizontal_bound: 0..50,
+        //         vertical_bound: 150..200,
+        //         continuation: vec![(4, 3), (1, 0), (0, 3), (3, 0)],
+        //     },
+        // ];
+
+        solve(Wrap3D::new(config, input), input)
     }
 }