AoC2021_11.java

import static java.util.stream.Collectors.joining;

import java.util.Arrays;
import java.util.List;

import com.github.pareronia.aoc.IntGrid;
import com.github.pareronia.aoc.Grid.Cell;
import com.github.pareronia.aoc.MutableInt;
import com.github.pareronia.aocd.Aocd;
import com.github.pareronia.aocd.Puzzle;

public class AoC2021_11 extends AoCBase {
    
    private final IntGrid grid;
    
    private AoC2021_11(final List<String> input, final boolean debug) {
        super(debug);
        this.grid = IntGrid.from(input);
    }
    
    private void printGrid() {
        if (!this.debug) {
            return;
        }
        Arrays.stream(this.grid.getValues()).forEach(r ->
                log(Arrays.stream(r)
                        .mapToObj(Integer::valueOf)
                        .map(String::valueOf)
                        .collect(joining(" "))));
    }

    public static final AoC2021_11 create(final List<String> input) {
        return new AoC2021_11(input, false);
    }

    public static final AoC2021_11 createDebug(final List<String> input) {
        return new AoC2021_11(input, true);
    }
    
    private void flash(final Cell c, final MutableInt flashes) {
        this.grid.setValue(c, 0);
        flashes.increment();
        this.grid.getAllNeighbours(c)
            .filter(n -> this.grid.getValue(n) != 0)
            .forEach(n -> {
                this.grid.increment(n);
                if (this.grid.getValue(n) > 9) {
                    flash(n, flashes);
                }
            });
    }
    
    private int cycle() {
        this.grid.getCells().forEach(this.grid::increment);
        final MutableInt flashes = new MutableInt(0);
        this.grid.getCells()
            .filter(c -> this.grid.getValue(c) > 9)
            .forEach(c -> flash(c, flashes));
        return flashes.intValue();
    }
    
    @Override
    public Integer solvePart1() {
        int cycle = 0;
        int flashes = 0;
        log("(" + cycle + ")");
        printGrid();
     
        for (cycle = 1; cycle <= 100; cycle++) {
            flashes += cycle();
            log("(" + cycle + ")");
            printGrid();
            log("flashes: " + flashes);
        }

        return flashes;
    }

    @Override
    public Integer solvePart2() {
        int cycle = 1;
        while (true) {
            final int flashes = cycle();
            if (flashes == this.grid.size()) {
                log("(" + cycle + ")");
                printGrid();
                log("flashes: " + flashes);
                break;
            }
            cycle++;
        }
        return cycle;
    }

    public static void main(final String[] args) throws Exception {
        assert AoC2021_11.create(TEST).solvePart1() == 1656;
        assert AoC2021_11.create(TEST).solvePart2() == 195;

        final Puzzle puzzle = Aocd.puzzle(2021, 11);
        puzzle.check(
            () -> lap("Part 1", () -> AoC2021_11.create(puzzle.getInputData()).solvePart1()),
            () -> lap("Part 2", () -> AoC2021_11.create(puzzle.getInputData()).solvePart2())
        );
    }

    private static final List<String> TEST = splitLines(
        "5483143223\r\n" +
        "2745854711\r\n" +
        "5264556173\r\n" +
        "6141336146\r\n" +
        "6357385478\r\n" +
        "4167524645\r\n" +
        "2176841721\r\n" +
        "6882881134\r\n" +
        "4846848554\r\n" +
        "5283751526"
    );
}