Day 22, part 1

src/bin/d22p1.rs

@@ -0,0 +1,18 @@
+use aoc22::{day22, util};
+
+pub fn main() {
+    let (grid, instructions) = day22::parse_map_and_path(&util::parse_input());
+
+    // dbg!(&grid);
+    // dbg!(&instructions);
+
+    let mut pose = day22::Pose::new(&grid);
+    // dbg!(&pose);
+    for inst in &instructions {
+        pose = day22::exec_instruction(&grid, &pose, inst);
+        // dbg!(&pose);
+    }
+
+    let pass = 1000 * (pose.pos.0 + 1) + 4 * (pose.pos.1 + 1) + (pose.orientation as usize);
+    println!("Passowrd: {}", pass);
+}

src/day22.rs

@@ -0,0 +1,188 @@
+use itertools::Itertools;
+
+use crate::util::Dir;
+
+#[derive(Debug)]
+pub enum TurnDir {
+    CW,
+    CCW,
+}
+
+#[derive(Debug)]
+pub enum Instruction {
+    Move(isize),
+    Turn(TurnDir),
+}
+
+#[derive(Debug)]
+pub struct Grid {
+    pub grid: Vec<Vec<Option<bool>>>,
+    pub height: usize,
+    pub width: usize,
+    pub row_bounds: Vec<(usize, usize)>,
+    pub col_bounds: Vec<(usize, usize)>,
+}
+
+pub fn parse_map_and_path(input: &str) -> (Grid, Vec<Instruction>) {
+    let lines = input.lines().collect_vec();
+
+    let mut grid: Vec<Vec<Option<bool>>> = Vec::new();
+    let mut width = 0;
+    for line in &lines[..lines.len() - 2] {
+        width = width.max(line.len());
+        let grid_line = line
+            .chars()
+            .map(|c| match c {
+                ' ' => None,
+                '.' => Some(false),
+                '#' => Some(true),
+                _ => panic!("Unknown grid character {}", c),
+            })
+            .collect();
+        grid.push(grid_line);
+    }
+
+    let height = grid.len();
+    let mut row_bounds = vec![(0, 0); height];
+    for row in 0..height {
+        let row_width = grid[row].len();
+        if row_width < width {
+            grid[row].extend((row_width..width).map(|_| None));
+        }
+        let lower = grid[row].iter().position(Option::is_some).unwrap();
+        let upper = width - 1 - grid[row].iter().rev().position(Option::is_some).unwrap();
+        row_bounds[row] = (lower, upper);
+    }
+
+    let mut col_bounds = vec![(0, 0); width];
+    for col in 0..width {
+        let col_it = (0..height).map(|row| grid[row][col]);
+        let lower = col_it.clone().position(|t| t.is_some()).unwrap();
+        let upper = height - 1 - col_it.rev().position(|t| t.is_some()).unwrap();
+        col_bounds[col] = (lower, upper);
+    }
+
+    let grid = Grid {
+        grid,
+        height,
+        width,
+        row_bounds,
+        col_bounds,
+    };
+
+    let mut instructions = Vec::new();
+    let mut inst_begin = 0;
+    let inst_line = lines[lines.len() - 1].as_bytes();
+    while inst_begin < inst_line.len() {
+        let mut i = inst_begin;
+        let c = inst_line[i];
+        if c.is_ascii_digit() {
+            while i < inst_line.len() && inst_line[i].is_ascii_digit() {
+                i += 1;
+            }
+            let dist = std::str::from_utf8(&inst_line[inst_begin..i])
+                .unwrap()
+                .parse()
+                .unwrap();
+            instructions.push(Instruction::Move(dist));
+            inst_begin = i;
+            continue;
+        }
+
+        let dir = match c {
+            b'L' => TurnDir::CCW,
+            b'R' => TurnDir::CW,
+            _ => panic!("Unknown turn direction {}", c),
+        };
+        instructions.push(Instruction::Turn(dir));
+        inst_begin += 1;
+    }
+
+    (grid, instructions)
+}
+
+#[derive(Debug)]
+pub struct Pose {
+    pub pos: (usize, usize),
+    pub orientation: Dir,
+}
+
+impl Pose {
+    pub fn new(grid: &Grid) -> Pose {
+        let col = grid.grid[0]
+            .iter()
+            .position(|t| if let Some(occ) = t { !occ } else { false })
+            .unwrap();
+        Pose {
+            pos: (0, col),
+            orientation: Dir::Right,
+        }
+    }
+}
+
+pub fn exec_instruction(grid: &Grid, pose: &Pose, instr: &Instruction) -> Pose {
+    match instr {
+        Instruction::Turn(turn_dir) => Pose {
+            pos: pose.pos,
+            orientation: match turn_dir {
+                TurnDir::CW => pose.orientation.cw(),
+                TurnDir::CCW => pose.orientation.ccw(),
+            },
+        },
+        Instruction::Move(n) => {
+            let mut pos = pose.pos;
+
+            for _ in 0..*n {
+                let next_pos = match pose.orientation {
+                    Dir::Left => {
+                        let bounds = &grid.row_bounds[pos.0];
+                        let next_col = if pos.1 == 0 || pos.1 == bounds.0 {
+                            bounds.1
+                        } else {
+                            pos.1 - 1
+                        };
+                        (pos.0, next_col)
+                    }
+                    Dir::Up => {
+                        let bounds = &grid.col_bounds[pos.1];
+                        let next_row = if pos.0 == 0 || pos.0 == bounds.0 {
+                            bounds.1
+                        } else {
+                            pos.0 - 1
+                        };
+                        (next_row, pos.1)
+                    }
+                    Dir::Right => {
+                        let bounds = &grid.row_bounds[pos.0];
+                        let next_col = if pos.1 == bounds.1 {
+                            bounds.0
+                        } else {
+                            pos.1 + 1
+                        };
+                        (pos.0, next_col)
+                    }
+                    Dir::Down => {
+                        let bounds = &grid.col_bounds[pos.1];
+                        let next_row = if pos.0 == bounds.1 {
+                            bounds.0
+                        } else {
+                            pos.0 + 1
+                        };
+                        (next_row, pos.1)
+                    }
+                };
+
+                if grid.grid[next_pos.0][next_pos.1].unwrap() {
+                    // We're about to hit a wall
+                    break;
+                }
+                pos = next_pos;
+            }
+
+            Pose {
+                pos,
+                orientation: pose.orientation,
+            }
+        }
+    }
+}

src/day9.rs

@@ -1,12 +1,6 @@
 use std::collections::HashSet;
 
-#[derive(Debug)]
+use crate::util::Dir;
-pub enum Dir {
-    Left,
-    Right,
-    Up,
-    Down,
-}
 
 pub type Motion = (Dir, usize);
 

src/lib.rs

@@ -12,6 +12,7 @@ pub mod day19;
 pub mod day2;
 pub mod day20;
 pub mod day21;
+pub mod day22;
 pub mod day3;
 pub mod day4;
 pub mod day5;

src/util.rs

@@ -122,3 +122,34 @@ where
 
     best
 }
+
+#[derive(Debug, Clone, Copy)]
+pub enum Dir {
+    Right = 0,
+    Down,
+    Left,
+    Up,
+}
+
+impl Dir {
+    pub fn from_usize(n: usize) -> Option<Dir> {
+        match n {
+            0 => Some(Dir::Right),
+            1 => Some(Dir::Down),
+            2 => Some(Dir::Left),
+            3 => Some(Dir::Up),
+            _ => None,
+        }
+    }
+
+    pub fn cw(&self) -> Dir {
+        let d = *self as usize;
+        Self::from_usize((d + 1) % 4).unwrap()
+    }
+
+    pub fn ccw(&self) -> Dir {
+        let d = *self as usize;
+        // Add 3 instead of subtracting one to avoid negative numbers
+        Self::from_usize((d + 3) % 4).unwrap()
+    }
+}