🏭 - 2024 DAY 15 SOLUTIONS - 🏭

CameronDev@programming.dev · 10 hours ago

🏭 - 2024 DAY 15 SOLUTIONS - 🏭

Gobbel2000@programming.dev · 2 hours ago

Rust

Part 2 was a bit tricky. Moving into a box horizontally works mostly the same as for part 1, for the vertical case I used two recursive functions. The first recurses from the left and right side for each box just to find out if the entire tree can be moved. The second function actually does the moving in a similar recursive structure, but now with the knowledge that all subtrees can actually be moved.

Lots of moving parts, but at least it could very nicely be debugged by printing out the map from the two minimal examples after each round.

Solution

use euclid::{default::*, vec2};

// Common type for both parts. In part 1 all boxes are BoxL.
#[derive(Clone, Copy)]
enum Spot {
    Empty,
    BoxL,
    BoxR,
    Wall,
}

impl From<u8> for Spot {
    fn from(value: u8) -> Self {
        match value {
            b'.' | b'@' => Spot::Empty,
            b'O' => Spot::BoxL,
            b'#' => Spot::Wall,
            other => panic!("Invalid spot: {other}"),
        }
    }
}

fn parse(input: &str) -> (Vec<Vec<Spot>>, Point2D<i32>, Vec<Vector2D<i32>>) {
    let (field_s, moves_s) = input.split_once("\n\n").unwrap();
    let mut field = Vec::new();
    let mut robot = None;
    for (y, l) in field_s.lines().enumerate() {
        let mut row = Vec::new();
        for (x, b) in l.bytes().enumerate() {
            row.push(Spot::from(b));
            if b == b'@' {
                robot = Some(Point2D::new(x, y).to_i32())
            }
        }
        field.push(row);
    }

    let moves = moves_s
        .bytes()
        .filter(|b| *b != b'\n')
        .map(|b| match b {
            b'^' => vec2(0, -1),
            b'>' => vec2(1, 0),
            b'v' => vec2(0, 1),
            b'<' => vec2(-1, 0),
            other => panic!("Invalid move: {other}"),
        })
        .collect();
    (field, robot.unwrap(), moves)
}

fn gps(field: &[Vec<Spot>]) -> u32 {
    let mut sum = 0;
    for (y, row) in field.iter().enumerate() {
        for (x, s) in row.iter().enumerate() {
            if let Spot::BoxL = s {
                sum += x + 100 * y;
            }
        }
    }
    sum as u32
}

fn part1(input: String) {
    let (mut field, mut robot, moves) = parse(&input);
    for m in moves {
        let next = robot + m;
        match field[next.y as usize][next.x as usize] {
            Spot::Empty => robot = next, // Move into space
            Spot::BoxL => {
                let mut search = next + m;
                let can_move = loop {
                    match field[search.y as usize][search.x as usize] {
                        Spot::BoxL => {}
                        Spot::Wall => break false,
                        Spot::Empty => break true,
                        Spot::BoxR => unreachable!(),
                    }
                    search += m;
                };
                if can_move {
                    robot = next;
                    field[next.y as usize][next.x as usize] = Spot::Empty;
                    field[search.y as usize][search.x as usize] = Spot::BoxL;
                }
            }
            Spot::Wall => {} // Cannot move
            Spot::BoxR => unreachable!(),
        }
    }
    println!("{}", gps(&field));
}

// Transform part 1 field to wider part 2 field
fn widen(field: &[Vec<Spot>]) -> Vec<Vec<Spot>> {
    field
        .iter()
        .map(|row| {
            row.iter()
                .flat_map(|s| match s {
                    Spot::Empty => [Spot::Empty; 2],
                    Spot::Wall => [Spot::Wall; 2],
                    Spot::BoxL => [Spot::BoxL, Spot::BoxR],
                    Spot::BoxR => unreachable!(),
                })
                .collect()
        })
        .collect()
}

// Recursively find out whether or not the robot can move in direction `dir` from `start`.
fn can_move_rec(field: &[Vec<Spot>], start: Point2D<i32>, dir: Vector2D<i32>) -> bool {
    let next = start + dir;
    match field[next.y as usize][next.x as usize] {
        Spot::Empty => true,
        Spot::BoxL => can_move_rec(field, next, dir) && can_move_rec(field, next + vec2(1, 0), dir),
        Spot::BoxR => can_move_rec(field, next - vec2(1, 0), dir) && can_move_rec(field, next, dir),
        Spot::Wall => false,
    }
}

// Recursively execute a move for vertical directions into boxes.
fn do_move(field: &mut [Vec<Spot>], start: Point2D<i32>, dir: Vector2D<i32>) {
    let next = start + dir;
    match field[next.y as usize][next.x as usize] {
        Spot::Empty | Spot::Wall => {}
        Spot::BoxL => {
            do_move(field, next, dir);
            do_move(field, next + vec2(1, 0), dir);
            let move_to = next + dir;
            field[next.y as usize][next.x as usize] = Spot::Empty;
            field[next.y as usize][next.x as usize + 1] = Spot::Empty;
            field[move_to.y as usize][move_to.x as usize] = Spot::BoxL;
            field[move_to.y as usize][move_to.x as usize + 1] = Spot::BoxR;
        }
        Spot::BoxR => {
            do_move(field, next - vec2(1, 0), dir);
            do_move(field, next, dir);
            let move_to = next + dir;
            field[next.y as usize][next.x as usize - 1] = Spot::Empty;
            field[next.y as usize][next.x as usize] = Spot::Empty;
            field[move_to.y as usize][move_to.x as usize - 1] = Spot::BoxL;
            field[move_to.y as usize][move_to.x as usize] = Spot::BoxR;
        }
    }
}

fn part2(input: String) {
    let (field1, robot1, moves) = parse(&input);
    let mut field = widen(&field1);
    let mut robot = Point2D::new(robot1.x * 2, robot1.y);
    for m in moves {
        let next = robot + m;
        match field[next.y as usize][next.x as usize] {
            Spot::Empty => robot = next, // Move into space
            Spot::BoxL | Spot::BoxR if m.y == 0 => {
                let mut search = next + m;
                let can_move = loop {
                    match field[search.y as usize][search.x as usize] {
                        Spot::BoxL | Spot::BoxR => {}
                        Spot::Wall => break false,
                        Spot::Empty => break true,
                    }
                    search += m;
                };
                if can_move {
                    robot = next;
                    // Shift boxes by array remove/insert
                    field[next.y as usize].remove(search.x as usize);
                    field[next.y as usize].insert(next.x as usize, Spot::Empty);
                }
            }
            Spot::BoxL | Spot::BoxR => {
                if can_move_rec(&field, robot, m) {
                    do_move(&mut field, robot, m);
                    robot = next;
                }
            }
            Spot::Wall => {} // Cannot move
        }
    }
    println!("{}", gps(&field));
}

util::aoc_main!();

Also on github

mykl@lemmy.world · edit-2 3 hours ago

Dart

canMove does a recursive search and returns all locations that need moving, or none if there’s an obstacle anywhere downstream. For part2, that involves checking if there’s half of a box in front of us, and if so ensuring that we also check the other half of that box. I don’t bother tracking whether we’re double-checking as it runs fast enough as is.

import 'dart:math';
import 'package:collection/collection.dart';
import 'package:more/more.dart';

var d4 = <Point<num>>[Point(1, 0), Point(-1, 0), Point(0, 1), Point(0, -1)];
var m4 = '><v^';

solve(List<String> lines, {wide = false}) {
  if (wide) {
    lines = lines
        .map((e) => e
            .replaceAll('#', '##')
            .replaceAll('.', '..')
            .replaceAll('O', '[]')
            .replaceAll('@', '@.'))
        .toList();
  }
  var room = {
    for (var r in lines.takeWhile((e) => e.isNotEmpty).indexed())
      for (var c in r.value.split('').indexed().where((c) => (c.value != '.')))
        Point<num>(c.index, r.index): c.value
  };
  var bot = room.entries.firstWhere((e) => e.value == '@').key;
  var moves = lines.skipTo('').join('').split('');
  for (var d in moves.map((m) => d4[m4.indexOf(m)])) {
    if (didMove(d, bot, room)) bot += d;
  }
  return room.entries
      .where((e) => e.value == '[' || e.value == 'O')
      .map((e) => e.key.x + 100 * e.key.y)
      .sum;
}

bool didMove(Point m, Point here, Map<Point, String> room) {
  var moves = canMove(m, here, room).toSet();
  if (moves.isNotEmpty) {
    var vals = moves.map((e) => room.remove(e)!).toList();
    for (var ms in moves.indexed()) {
      room[ms.value + m] = vals[ms.index];
    }
    return true;
  }
  return false;
}

List<Point> canMove(Point m, Point here, Map<Point, String> room) {
  if (room[here + m] == '#') return [];
  if (!room.containsKey(here + m)) return [here];
  var cm1 = canMove(m, here + m, room);
  if (m.x != 0) return (cm1.isEmpty) ? [] : cm1 + [here];

  List<Point> cm2 = [here];
  if (room[here + m] == '[') cm2 = canMove(m, here + m + Point(1, 0), room);
  if (room[here + m] == ']') cm2 = canMove(m, here + m - Point(1, 0), room);

  return cm1.isEmpty || cm2.isEmpty ? [] : cm1 + cm2 + [here];
}

JRaccoon · 5 hours ago

TypeScript

Not very optimized code today. Basically just a recursive function

Code

import fs from "fs";

type Point = {x: number, y: number};

enum Direction {
    UP = '^',
    DOWN = 'v',
    LEFT = '<',
    RIGHT = '>'
}

const input = fs.readFileSync("./15/input.txt", "utf-8").split(/[\r\n]{4,}/);
const warehouse: string[][] = input[0]
    .split(/[\r\n]+/)
    .map(row => row.split(""));
const movements: Direction[] = input[1]
    .split("")
    .map(char => char.trim())
    .filter(Boolean)
    .map(char => char as Direction);

// Part 1
console.info("Part 1: " + solve(warehouse, movements));

// Part 2
const secondWarehouse = warehouse.map(row => {
    const newRow: string[] = [];
    for (const char of row) {
        if (char === '#') { newRow.push('#', '#'); }
        else if (char === 'O') { newRow.push('[', ']'); }
        else if (char === '.') { newRow.push('.', '.'); }
        else { newRow.push('@', '.'); }
    }
    return newRow;
});
console.info("Part 2: " + solve(secondWarehouse, movements));

function solve(warehouse: string[][], movements: Direction[]): number {
    let _warehouse = warehouse.map(row => [...row]); // Take a copy to avoid modifying the original
    const robotLocation: Point = findStartLocation(_warehouse);

    for (const move of movements) {
        // Under some very specific circumstances in part 2, tryMove returns false, but the grid has already been modified
        // "Fix" the issue ba taking a copy so we can easily revert all changes made
        // Slow AF of course but rest of this code isn't optimized either, so...
        const copy = _warehouse.map(row => [...row]);
    
        if (tryMove(robotLocation, move, _warehouse)) {
            if (move === Direction.UP) { robotLocation.y--; }
            else if (move === Direction.DOWN) { robotLocation.y++; }
            else if (move === Direction.LEFT) { robotLocation.x--; }
            else { robotLocation.x++; }
        } else {
            _warehouse = copy; // Revert changes
        }
    }

    // GPS
    let result = 0;
    for (let y = 0; y < _warehouse.length; y++) {
        for (let x = 0; x < _warehouse[y].length; x++) {
            if (_warehouse[y][x] === "O" || _warehouse[y][x] === "[") {
                result += 100 * y + x;
            }
        }
    }
    return result;
}

function tryMove(from: Point, direction: Direction, warehouse: string[][], movingPair = false): boolean {
    const moveWhat = warehouse[from.y][from.x];
    if (moveWhat === "#") {
        return false;
    }

    let to: Point;
    switch (direction) {
        case Direction.UP: to = {x: from.x, y: from.y - 1}; break;
        case Direction.DOWN: to = {x: from.x, y: from.y + 1}; break;
        case Direction.LEFT: to = {x: from.x - 1, y: from.y}; break;
        case Direction.RIGHT: to = {x: from.x + 1, y: from.y}; break;
    }

    const allowMove = warehouse[to.y][to.x] === "."
        || (direction === Direction.UP && tryMove({x: from.x, y: from.y - 1}, direction, warehouse))
        || (direction === Direction.DOWN && tryMove({x: from.x, y: from.y + 1}, direction, warehouse))
        || (direction === Direction.LEFT && tryMove({x: from.x - 1, y: from.y}, direction, warehouse))
        || (direction === Direction.RIGHT && tryMove({x: from.x + 1, y: from.y}, direction, warehouse));

    if (allowMove) {
        // Part 1 logic handles horizontal movement of larger boxes just fine. Needs special handling for vertical movement
        if (!movingPair && (direction === Direction.UP || direction === Direction.DOWN)) {
            if (moveWhat === "[" && !tryMove({x: from.x + 1, y: from.y}, direction, warehouse, true)) {
                return false;
            }
            if (moveWhat === "]" && !tryMove({x: from.x - 1, y: from.y}, direction, warehouse, true)) {
                return false;
            }
        }

        // Make the move
        warehouse[to.y][to.x] = moveWhat;
        warehouse[from.y][from.x] = ".";
        return true;
    }
    return false;
}

function findStartLocation(warehouse: string[][]): Point {
    for (let y = 0; y < warehouse.length; y++) {
        for (let x = 0; x < warehouse[y].length; x++) {
            if (warehouse[y][x] === "@") {
                return {x,y};
            }
        }
    }

    throw new Error("Could not find start location!");
}

janAkali@lemmy.one · 7 hours ago

Nim

Very fiddly solution with lots of debugging required.

Code

type
  Vec2 = tuple[x,y: int]
  Box = array[2, Vec2]
  Dir = enum
    U = "^"
    R = ">"
    D = "v"
    L = "<"

proc convertPart2(grid: seq[string]): seq[string] =
  for y in 0..grid.high:
    result.add ""
    for x in 0..grid[0].high:
      result[^1] &= (
        if grid[y][x] == 'O': "[]"
        elif grid[y][x] == '#': "##"
        else: "..")

proc shiftLeft(grid: var seq[string], col: int, range: HSlice[int,int]) =
  for i in range.a ..< range.b:
    grid[col][i] = grid[col][i+1]
  grid[col][range.b] = '.'

proc shiftRight(grid: var seq[string], col: int, range: HSlice[int,int]) =
  for i in countDown(range.b, range.a+1):
    grid[col][i] = grid[col][i-1]
  grid[col][range.a] = '.'

proc box(pos: Vec2, grid: seq[string]): array[2, Vec2] =
  if grid[pos.y][pos.x] == '[':
    [pos, (pos.x+1, pos.y)]
  else:
    [(pos.x-1, pos.y), pos]

proc step(grid: var seq[string], bot: var Vec2, dir: Dir) =
  var (x, y) = bot
  case dir
  of U:
    while (dec y; grid[y][x] != '#' and grid[y][x] != '.'): discard
    if grid[y][x] == '#': return
    if grid[bot.y-1][bot.x] == 'O': swap(grid[bot.y-1][bot.x], grid[y][x])
    dec bot.y
  of R:
    while (inc x; grid[y][x] != '#' and grid[y][x] != '.'): discard
    if grid[y][x] == '#': return
    if grid[bot.y][bot.x+1] == 'O': swap(grid[bot.y][bot.x+1], grid[y][x])
    inc bot.x
  of L:
    while (dec x; grid[y][x] != '#' and grid[y][x] != '.'): discard
    if grid[y][x] == '#': return
    if grid[bot.y][bot.x-1] == 'O': swap(grid[bot.y][bot.x-1], grid[y][x])
    dec bot.x
  of D:
    while (inc y; grid[y][x] != '#' and grid[y][x] != '.'): discard
    if grid[y][x] == '#': return
    if grid[bot.y+1][bot.x] == 'O': swap(grid[bot.y+1][bot.x], grid[y][x])
    inc bot.y

proc canMoveVert(box: Box, grid: seq[string], boxes: var HashSet[Box], dy: int): bool =
  boxes.incl box
  var left, right = false
  let (lbox, rbox) = (box[0], box[1])
  let lbigBox = box((lbox.x, lbox.y+dy), grid)
  let rbigBox = box((rbox.x, lbox.y+dy), grid)

  if grid[lbox.y+dy][lbox.x] == '#' or
     grid[rbox.y+dy][rbox.x] == '#': return false
  elif grid[lbox.y+dy][lbox.x] == '.': left = true
  else:
    left = canMoveVert(box((lbox.x,lbox.y+dy), grid), grid, boxes, dy)

  if grid[rbox.y+dy][rbox.x] == '.': right = true
  elif lbigBox == rbigBox: right = left
  else:
    right = canMoveVert(box((rbox.x, rbox.y+dy), grid), grid, boxes, dy)

  left and right

proc moveBoxes(grid: var seq[string], boxes: var HashSet[Box], d: Vec2) =
  for box in boxes:
    grid[box[0].y][box[0].x] = '.'
    grid[box[1].y][box[1].x] = '.'
  for box in boxes:
    grid[box[0].y+d.y][box[0].x+d.x] = '['
    grid[box[1].y+d.y][box[1].x+d.x] = ']'
  boxes.clear()

proc step2(grid: var seq[string], bot: var Vec2, dir: Dir) =
  case dir
  of U:
    if grid[bot.y-1][bot.x] == '#': return
    if grid[bot.y-1][bot.x] == '.': dec bot.y
    else:
      var boxes: HashSet[Box]
      if canMoveVert(box((x:bot.x, y:bot.y-1), grid), grid, boxes, -1):
        grid.moveBoxes(boxes, (0, -1))
        dec bot.y
  of R:
    var (x, y) = bot
    while (inc x; grid[y][x] != '#' and grid[y][x] != '.'): discard
    if grid[y][x] == '#': return
    if grid[bot.y][bot.x+1] == '[': grid.shiftRight(bot.y, bot.x+1..x)
    inc bot.x
  of L:
    var (x, y) = bot
    while (dec x; grid[y][x] != '#' and grid[y][x] != '.'): discard
    if grid[y][x] == '#': return
    if grid[bot.y][bot.x-1] == ']': grid.shiftLeft(bot.y, x..bot.x-1)
    dec bot.x
  of D:
    if grid[bot.y+1][bot.x] == '#': return
    if grid[bot.y+1][bot.x] == '.': inc bot.y
    else:
      var boxes: HashSet[Box]
      if canMoveVert(box((x:bot.x, y:bot.y+1), grid), grid, boxes, 1):
        grid.moveBoxes(boxes, (0, 1))
        inc bot.y


proc solve(input: string): AOCSolution[int, int] =
  let chunks = input.split("\n\n")
  var grid = chunks[0].splitLines()
  let movements = chunks[1].splitLines().join().join()

  var robot: Vec2
  for y in 0..grid.high:
    for x in 0..grid[0].high:
      if grid[y][x] == '@':
        grid[y][x] = '.'
        robot = (x,y)

  block p1:
    var grid = grid
    var robot = robot
    for m in movements:
      let dir = parseEnum[Dir]($m)
      step(grid, robot, dir)
    for y in 0..grid.high:
      for x in 0..grid[0].high:
        if grid[y][x] == 'O':
          result.part1 += 100 * y + x

  block p2:
    var grid = grid.convertPart2()
    var robot = (robot.x*2, robot.y)
    for m in movements:
      let dir = parseEnum[Dir]($m)
      step2(grid, robot, dir)
      #grid.inspect(robot)

    for y in 0..grid.high:
      for x in 0..grid[0].high:
        if grid[y][x] == '[':
          result.part2 += 100 * y + x

Codeberg Repo

lwhjp@lemmy.sdf.org · 8 hours ago

Haskell

This was a fun one! I’m quite pleased with moveInto, which could be easily extended to support arbitrary box shapes.

Solution

import Control.Monad
import Data.Bifunctor
import Data.List
import Data.Map (Map)
import Data.Map qualified as Map
import Data.Set (Set)
import Data.Set qualified as Set

type C = (Int, Int)

readInput :: String -> (Map C Char, [C])
readInput s =
  let (room, _ : moves) = break null $ lines s
   in ( Map.fromList [((i, j), c) | (i, l) <- zip [0 ..] room, (j, c) <- zip [0 ..] l],
        map dir $ concat moves
      )
  where
    dir '^' = (-1, 0)
    dir 'v' = (1, 0)
    dir '<' = (0, -1)
    dir '>' = (0, 1)

moveInto :: Int -> Set C -> C -> C -> Set C -> Maybe (Set C)
moveInto boxWidth walls (di, dj) = go
  where
    go (i, j) boxes
      | (i, j) `Set.member` walls = Nothing
      | Just j' <- find (\j' -> (i, j') `Set.member` boxes) $ map (j -) [0 .. boxWidth - 1] =
          Set.insert (i + di, j' + dj)
            <$> foldM
              (flip go)
              (Set.delete (i, j') boxes)
              [(i + di, j' + z + dj) | z <- [0 .. boxWidth - 1]]
      | otherwise = Just boxes

runMoves :: (Map C Char, [C]) -> Int -> Int
runMoves (room, moves) scale = score $ snd $ foldl' move (start, boxes) moves
  where
    room' = Map.mapKeysMonotonic (second (* scale)) room
    Just start = fst <$> find ((== '@') . snd) (Map.assocs room')
    walls =
      let ps = Map.keysSet $ Map.filter (== '#') room'
       in Set.unions [Set.mapMonotonic (second (+ z)) ps | z <- [0 .. scale - 1]]
    boxes = Map.keysSet $ Map.filter (== 'O') room'
    move (pos@(i, j), boxes) dir@(di, dj) =
      let pos' = (i + di, j + dj)
       in maybe (pos, boxes) (pos',) $ moveInto scale walls dir pos' boxes
    score = sum . map (\(i, j) -> i * 100 + j) . Set.elems

main = do
  input <- readInput <$> readFile "input15"
  mapM_ (print . runMoves input) [1, 2]

M	T	W	T	F	S	S
						1
2	3	4	5	6	7	8
9	10	11	12	13	14	15
16	17	18	18	20	21	22
23	24	25

🏭 - 2024 DAY 15 SOLUTIONS - 🏭

🏭 - 2024 DAY 15 SOLUTIONS - 🏭

Day 15: Warehouse Woes

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FAQ

Rust

Dart

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Haskell