Day 11: Flashing octopi - detonating neighbours' flashes

Author: Inusette

Advent_2021/src/main/java/Day11/Day11Main.java

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+package Day11;
+
+import advent.utils.AdventFileUtils;
+
+import java.util.List;
+
+public class Day11Main {
+
+    public static void main(String[] args) {
+        List<List<Integer>> inputAsMatrix = getInput();
+        inputAsMatrix.forEach(System.out::println);
+
+        OctopusDetonator octopusDetonator = new OctopusDetonator();
+        long octopusFlashes = octopusDetonator.detonateOctopusFlashes(inputAsMatrix);
+        System.out.println(octopusFlashes);
+
+        long allFlashingStep = octopusDetonator.findAllFlashingStep(inputAsMatrix);
+        System.out.println(allFlashingStep);
+    }
+
+    protected static List<List<Integer>> getInput() {
+        return AdventFileUtils.readClassInputIntoIntegerMatrix(Day11Main.class);
+    }
+}

Advent_2021/src/main/java/Day11/OctopusDetonator.java

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+package Day11;
+
+import java.awt.*;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+public class OctopusDetonator {
+
+    private final int GRID_MAX = 10;
+
+    public long detonateOctopusFlashes(List<List<Integer>> octopuses) {
+        int step = 0;
+        long flashCount = 0;
+        while (step != 100) {
+            incrementEnergy(octopuses);
+
+            Set<Point> flashed = getFlashedOctopuses(octopuses);
+            flashed.forEach(flash -> octopuses.get(flash.y).set(flash.x, 0));
+            flashCount += flashed.size();
+            step++;
+        }
+        return flashCount;
+    }
+
+    public long findAllFlashingStep(List<List<Integer>> octopuses) {
+        int step = 0;
+        long flashCount = 0;
+        while (flashCount != 100) {
+            incrementEnergy(octopuses);
+            Set<Point> flashed = getFlashedOctopuses(octopuses);
+            flashed.forEach(flash -> octopuses.get(flash.y).set(flash.x, 0));
+            flashCount = flashed.size();
+            step++;
+        }
+        return step;
+    }
+
+    private Set<Point> getFlashedOctopuses(List<List<Integer>> octopuses) {
+        Set<Point> flashed = new HashSet<>();
+        for (int row = 0; row < GRID_MAX; row++) {
+            for (int column = 0; column < GRID_MAX; column++) {
+                Integer octopusEnergy = octopuses.get(row).get(column);
+                if (octopusEnergy > 9) {
+                    flash(octopuses, new Point(column, row), flashed);
+                }
+            }
+        }
+        return flashed;
+    }
+
+    private void incrementEnergy(List<List<Integer>> octopuses) {
+        for (int row = 0; row < GRID_MAX; row++) {
+            for (int column = 0; column < GRID_MAX; column++) {
+                octopuses.get(row).set(column, octopuses.get(row).get(column) + 1);
+            }
+        }
+    }
+
+    private void flash(List<List<Integer>> octopuses, Point flash, Set<Point> flashed) {
+        if (flashed.contains(flash)) {
+            return;
+        }
+        flashed.add(flash);
+
+        Set<Point> neighbours = getNeighbours(flash);
+        for (Point neighbour : neighbours) {
+            Integer neighbourEnergy = octopuses.get(neighbour.y).get(neighbour.x);
+            neighbourEnergy++;
+            octopuses.get(neighbour.y).set(neighbour.x, neighbourEnergy);
+            if (neighbourEnergy > 9) {
+                flash(octopuses, neighbour, flashed);
+            }
+        }
+    }
+
+    private Set<Point> getNeighbours(Point flash) {
+        Set<Point> neighbours = new HashSet<>();
+        if (flash.x > 0) {
+            // left neighbour
+            neighbours.add(new Point(flash.x - 1, flash.y));
+            if (flash.y > 0) {
+                // left Neighbour Above
+                neighbours.add(new Point(flash.x - 1, flash.y - 1));
+            }
+            if (flash.y < GRID_MAX - 1) {
+                //left Neighbour Below
+                neighbours.add(new Point(flash.x - 1, flash.y + 1));
+            }
+        }
+        if (flash.x < GRID_MAX - 1) {
+            // right Neighbour
+            neighbours.add(new Point(flash.x + 1, flash.y));
+            if (flash.y > 0) {
+                // right Neighbour Above
+                neighbours.add(new Point(flash.x + 1, flash.y - 1));
+            }
+            if (flash.y < GRID_MAX - 1) {
+                // right Neighbour Below
+                neighbours.add(new Point(flash.x + 1, flash.y + 1));
+            }
+        }
+        if (flash.y > 0) {
+            // above Neighbour
+            neighbours.add(new Point(flash.x, flash.y - 1));
+        }
+        if (flash.y < GRID_MAX - 1) {
+            // below Neighbour
+            neighbours.add(new Point(flash.x, flash.y + 1));
+        }
+        return neighbours;
+    }
+}

Advent_2021/src/main/resources/Day11/input.txt

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+4738615556
+6744423741
+2812868827
+8844365624
+4546674266
+4518674278
+7457237431
+4524873247
+3153341314
+3721414667