Day14.java

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

/**
 * @author Zachary Cockshutt
 * @since  2023-12-14
 */
public class Day14 extends Day
{
    private static final Direction N = Direction.N, S = Direction.S,
                                   E = Direction.E, W = Direction.W;

    @Override
    public String partOne() throws IOException
    {
        var platform = this.parsePlatform();
        platform.tilt(N);
        var load = platform.getLoad();
        return String.valueOf(load);
    }

    @Override
    public String partTwo() throws IOException
    {
        var platform = this.parsePlatform();
        for (int i = 0; i < 1000; i++)
        {
            platform.tilt(N);
            platform.tilt(W);
            platform.tilt(S);
            platform.tilt(E);
        }
        var load = platform.getLoad();
        return String.valueOf(load);
    }

    private Platform parsePlatform() throws IOException
    {
        var matrix = new ArrayList<char[]>();
        this.input((s) -> matrix.add(s.toCharArray()));
        return new Platform(matrix.toArray(new char[matrix.size()][]));
    }

    private record Platform(char[][] matrix)
    {
        private void tilt(Direction dir)
        {
            var rows = IntStream.range(0, matrix.length).boxed().collect(Collectors.toCollection(ArrayList::new));
            var cols = IntStream.range(0, matrix[0].length).boxed().collect(Collectors.toCollection(ArrayList::new));
            if (dir == S) { Collections.reverse(rows); }
            if (dir == E) { Collections.reverse(cols); }
            for (int i : rows)
                for (int j : cols)
                    if (matrix[i][j] == 'O')
                    {
                        int y = i+dir.y, x = j+dir.x;
                        while (y>=0 && y<matrix.length
                            && x>=0 && x<matrix[0].length
                            && matrix[y][x] == '.')
                        {
                            matrix[y-dir.y][x-dir.x] = '.';
                            matrix[y][x] = 'O';
                            x += dir.x;
                            y += dir.y;
                        }
                    }
        }

        private int getLoad()
        {
            int load = 0;
            for (int i=0; i<matrix.length; i++)
                for (int j=0; j<matrix[0].length; j++)
                    if (matrix[i][j] == 'O') { load += matrix.length-i; }
            return load;
        }
    }

    private static enum Direction
    {
        N(0,-1), S(0, 1), E(1, 0), W(-1,0);
        private final int x, y;
        Direction(int x, int y) { this.x = x; this.y = y; }
    }
}