Day 22 2022

1 files changed, 314 insertions, 0 deletions

diff --git a/2022/22/b.rs b/2022/22/b.rs
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+use std::mem::swap;
+mod common;
+use common::*;
+
+// Use 4 for the test input, 50 for the real one
+//const CUBE_SIZE: usize = 4;
+const CUBE_SIZE: usize = 50;
+
+// Connections between faces to make the cube 3D.
+// This is hard coded to work for my specific input.
+// To make it work for a different input you have to change this.
+// The faces are in top-to-bottom, left-to-right order of input.
+// For each face, the 4 connections are in order right, down, left, up.
+
+// Test case. Configuration:
+//   0     U = 0, D = 4
+// 123     R = 5, L = 2
+//   45    F = 3, B = 1
+/*
+const CONNECTIONS: [[Connection; 4]; 6] = [
+    // Face 0 = U
+    [
+        Connection { face: 5, side: Direction::Right },
+        Connection { face: 3, side: Direction::Up },
+        Connection { face: 2, side: Direction::Up },
+        Connection { face: 1, side: Direction::Up },
+    ],
+
+    // Face 1
+    [
+        Connection { face: 2, side: Direction::Left },
+        Connection { face: 4, side: Direction::Down },
+        Connection { face: 5, side: Direction::Down },
+        Connection { face: 0, side: Direction::Up },
+    ],
+
+    // Face 2
+    [
+        Connection { face: 3, side: Direction::Left },
+        Connection { face: 4, side: Direction::Left },
+        Connection { face: 1, side: Direction::Right },
+        Connection { face: 0, side: Direction::Left },
+    ],
+
+    // Face 3
+    [
+        Connection { face: 5, side: Direction::Up },
+        Connection { face: 4, side: Direction::Up },
+        Connection { face: 2, side: Direction::Right },
+        Connection { face: 0, side: Direction::Down },
+    ],
+
+    // Face 4
+    [
+        Connection { face: 5, side: Direction::Left },
+        Connection { face: 1, side: Direction::Down },
+        Connection { face: 2, side: Direction::Down },
+        Connection { face: 3, side: Direction::Down },
+    ],
+
+    // Face 5
+    [
+        Connection { face: 0, side: Direction::Right },
+        Connection { face: 1, side: Direction::Left },
+        Connection { face: 4, side: Direction::Right },
+        Connection { face: 3, side: Direction::Right },
+    ],
+];
+*/
+
+// Input. Configuration:
+//  01
+//  2 
+// 34
+// 5
+const CONNECTIONS: [[Connection; 4]; 6] = [
+    // Face 0 = U
+    [
+        Connection { face: 1, side: Direction::Left },
+        Connection { face: 2, side: Direction::Up },
+        Connection { face: 3, side: Direction::Left },
+        Connection { face: 5, side: Direction::Left },
+    ],
+
+    // Face 1
+    [
+        Connection { face: 4, side: Direction::Right },
+        Connection { face: 2, side: Direction::Right },
+        Connection { face: 0, side: Direction::Right },
+        Connection { face: 5, side: Direction::Down },
+    ],
+
+    // Face 2
+    [
+        Connection { face: 1, side: Direction::Down },
+        Connection { face: 4, side: Direction::Up },
+        Connection { face: 3, side: Direction::Up },
+        Connection { face: 0, side: Direction::Down },
+    ],
+
+    // Face 3
+    [
+        Connection { face: 4, side: Direction::Left },
+        Connection { face: 5, side: Direction::Up },
+        Connection { face: 0, side: Direction::Left },
+        Connection { face: 2, side: Direction::Left },
+    ],
+
+    // Face 4
+    [
+        Connection { face: 1, side: Direction::Right },
+        Connection { face: 5, side: Direction::Right },
+        Connection { face: 3, side: Direction::Right },
+        Connection { face: 2, side: Direction::Down },
+    ],
+
+    // Face 5
+    [
+        Connection { face: 4, side: Direction::Down },
+        Connection { face: 1, side: Direction::Up },
+        Connection { face: 0, side: Direction::Up },
+        Connection { face: 3, side: Direction::Down },
+    ],
+];
+
+
+#[derive(Copy, Clone, Debug)]
+struct Connection {
+    pub face: usize,
+    pub side: Direction
+}
+
+struct Face {
+    pub tiles: [[Tile; CUBE_SIZE]; CUBE_SIZE],
+    offset_i: usize,
+    offset_j: usize
+}
+
+#[derive(PartialEq, Debug, Copy, Clone)]
+struct Position {
+    f: usize,
+    i: usize,
+    j: usize,
+    d: Direction
+}
+
+#[allow(dead_code)]
+impl Face {
+    pub fn empty() -> Face {
+        Face {
+            tiles: [[Tile::Skip; CUBE_SIZE]; CUBE_SIZE],
+            offset_i: 0,
+            offset_j: 0
+        }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.tiles[0][0] == Tile::Skip
+    }
+
+    pub fn print(&self) {
+        for i in 0..CUBE_SIZE {
+            for j in 0..CUBE_SIZE {
+                print!("{}", self.tiles[i][j].to_char());
+            }
+            println!();
+        }
+    }
+}
+
+struct Cube {
+    pub faces: Vec<Face>
+}
+
+type StepFn = fn(&Cube, Position) -> Position;
+
+impl Cube {
+    pub fn from_stdin() -> Cube {
+        let mut faces = vec![];
+        let mut line = String::new();
+        let mut offset_i = 0;
+        while faces.len() < 6 {
+            let mut row = [Face::empty(), Face::empty(), Face::empty(),
+                           Face::empty(), Face::empty(), Face::empty()];
+            for k in 0..CUBE_SIZE {
+                let _ = std::io::stdin().read_line(&mut line);
+                let bytes = &line.as_bytes();
+                for l in 0..line.len()-1 {
+                    row[l / CUBE_SIZE].tiles[k][l % CUBE_SIZE] =
+                        Tile::from_byte(bytes[l]);
+                }
+                line.clear();
+            }
+            let mut offset_j = 0;
+            for mut r in row {
+                r.offset_i = offset_i;
+                r.offset_j = offset_j;
+                if !r.is_empty() {
+                    faces.push(r);
+                }
+                offset_j += CUBE_SIZE;
+            }
+            offset_i += CUBE_SIZE;
+        }
+        let _ = std::io::stdin().read_line(&mut line); // Read empty line
+        assert!(faces.len() == 6, "Cube has {} faces", faces.len());
+        Cube { faces }
+    }
+
+    fn start_position(&self) -> Position {
+        let j = self.faces[0].tiles[0].iter()
+            .position(|t| *t == Tile::Walk).unwrap();
+        Position { f: 0, i: 0, j, d: Direction::Right }
+    }
+
+    pub fn walk(&self, pos: Position, n: usize, step: StepFn) -> Position {
+        let mut p = pos;
+        for _ in 0..n { p = step(self, p); }
+        p
+    }
+}
+
+fn flips(d1: Direction, d2: Direction) -> bool {
+    match d1 {
+        Direction::Right | Direction::Up =>
+            d2 == Direction::Right || d2 == Direction::Up,
+        Direction::Down | Direction::Left =>
+            d2 == Direction::Down || d2 == Direction::Left
+    }
+}
+
+fn swaps(d1: Direction, d2: Direction) -> bool {
+    match d1 {
+        Direction::Right | Direction::Left =>
+            d2 == Direction::Up || d2 == Direction::Down,
+        Direction::Up | Direction::Down =>
+            d2 == Direction::Right || d2 == Direction::Left
+    }
+}
+
+fn validate_connections(conn: &[[Connection; 4]; 6]) {
+    for i in 0..6 {
+        for j in 0..4 {
+            let c = conn[i][j];
+            let d = conn[c.face][c.side.value()];
+            assert!(d.face == i, "Bad connection: face {}-{}", i, j);
+            assert!(d.side.value() == j, "Bad connection: side {}-{}", i, j);
+        }
+    }
+}
+
+fn overflow(i: i64, j: i64) -> Option<Direction> {
+    if i == -1 { return Some(Direction::Up) }
+    if j == -1 { return Some(Direction::Left) }
+    if i as usize == CUBE_SIZE { return Some(Direction::Down) }
+    if j as usize == CUBE_SIZE { return Some(Direction::Right) }
+    None
+}
+
+fn on_other_side(i: i64, flip: bool, positive: bool) -> usize {
+    const CUBE_SIZE_I64: i64 = CUBE_SIZE as i64;
+    (if i >= 0 && i < CUBE_SIZE_I64 {
+        if flip { CUBE_SIZE_I64 - i - 1 } else { i }
+    } else {
+        if positive { 0 } else { CUBE_SIZE_I64 - 1 }
+    }) as usize
+}
+
+fn step(cube: &Cube, p: Position) -> Position {
+    let s = p.d.step();
+    let mut inext = s.0 + p.i as i64;
+    let mut jnext = s.1 + p.j as i64;
+
+    let ret = if let Some(d) = overflow(inext, jnext) {
+        let conn = CONNECTIONS[p.f][d.value()];
+        let flip = flips(p.d, conn.side);
+        let new_direction = conn.side.opposite();
+        let positive = new_direction.is_positive();
+        if swaps(p.d, conn.side) { swap(&mut inext, &mut jnext) }
+        Position {
+            f: conn.face,
+            i: on_other_side(inext, flip, positive),
+            j: on_other_side(jnext, flip, positive),
+            d: conn.side.opposite()
+        }
+    } else {
+        Position {
+            f: p.f,
+            i: inext as usize,
+            j: jnext as usize,
+            d: p.d
+        }
+    };
+
+    if cube.faces[ret.f].tiles[ret.i][ret.j] == Tile::Wall { p } else { ret }
+}
+
+fn password(cube: &Cube, p: Position) -> usize {
+    let f = &cube.faces[p.f];
+    1000 * (p.i + f.offset_i + 1) + 4 * (p.j + f.offset_j + 1) + p.d.value()
+}
+
+fn main() {
+    validate_connections(&CONNECTIONS);
+    let cube = Cube::from_stdin();
+    let mut position = cube.start_position();
+    let (turns, steps) = read_instruction_line_from_stdin();
+    for i in 0..turns.len() {
+        position = cube.walk(position, steps[i], step);
+        position.d = position.d.turn(turns[i]);
+    }
+    position = cube.walk(position, steps[steps.len()-1], step);
+    println!("{}", password(&cube, position));
+}