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Day 19
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‎src/test/java/com/macasaet/Day19.java

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package com.macasaet;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import java.util.*;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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import java.util.stream.StreamSupport;
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import org.junit.jupiter.api.Nested;
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import org.junit.jupiter.api.Test;
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/**
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* --- Day 19: Beacon Scanner ---
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*/
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public class Day19 {
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protected Stream<String> getInput() {
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return StreamSupport
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.stream(new LineSpliterator("day-19.txt"),
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false);
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}
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protected List<Scanner> getScanners() {
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final var list = getInput().toList();
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final var result = new ArrayList<Scanner>();
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var observations = new HashSet<Position>();
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int id = -1;
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for (final var line : list) {
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if (line.startsWith("--- scanner ")) {
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id = Integer.parseInt(line
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.replaceFirst("^--- scanner ", "")
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.replaceFirst(" ---$", ""));
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} else if (!line.isBlank()) {
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observations.add(Position.parse(line));
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} else { // line is blank
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result.add(new Scanner(id, Collections.unmodifiableSet(observations)));
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observations = new HashSet<>();
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id = -1;
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}
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}
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result.add(new Scanner(id, Collections.unmodifiableSet(observations)));
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return Collections.unmodifiableList(result);
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}
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public enum Direction {
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POSITIVE_X {
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public Position face(Position position) {
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return position;
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}
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},
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NEGATIVE_X {
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public Position face(Position position) {
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return new Position(-position.x(), position.y(), -position.z());
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}
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},
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POSITIVE_Y {
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public Position face(Position position) {
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return new Position(position.y(), -position.x(), position.z());
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}
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},
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NEGATIVE_Y {
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public Position face(Position position) {
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return new Position(-position.y(), position.x(), position.z());
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}
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},
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POSITIVE_Z {
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public Position face(Position position) {
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return new Position(position.z(), position.y(), -position.x());
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}
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},
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NEGATIVE_Z {
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public Position face(Position position) {
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return new Position(-position.z(), position.y(), position.x());
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}
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};
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public abstract Position face(final Position position);
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}
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public enum Rotation {
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r0 {
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public Position rotate(final Position position) {
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return position;
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}
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},
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r90 {
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public Position rotate(Position position) {
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return new Position(position.x(), -position.z(), position.y());
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}
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},
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r180 {
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public Position rotate(Position position) {
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return new Position(position.x(), -position.y(), -position.z());
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}
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},
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r270 {
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public Position rotate(Position position) {
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return new Position(position.x(), position.z(), -position.y());
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}
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};
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public abstract Position rotate(final Position position);
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}
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public record Transformation(Direction direction, Rotation rotation) {
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/**
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* Look at a position from a specific orientation
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*
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* @param position a position relative to one point of view
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* @return the same position relative to a different point of view
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*/
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public Position reorient(final Position position) {
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return rotation.rotate(direction.face(position));
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}
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}
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public record Position(int x, int y, int z) {
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public static Position parse(final String line) {
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final var components = line.split(",");
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return new Position(Integer.parseInt(components[0]),
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Integer.parseInt(components[1]),
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Integer.parseInt(components[2]));
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}
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public Position plus(Position amount) {
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return new Position(x() + amount.x(), y() + amount.y(), z() + amount.z());
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}
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public Position minus(final Position other) {
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return new Position(x() - other.x(), y() - other.y(), z() - other.z());
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}
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}
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public interface OverlapResult {
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}
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public record Overlap(Position distance, Transformation transformation,
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Set<Position> overlappingBeacons) implements OverlapResult {
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}
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public record None() implements OverlapResult {
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}
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public record Scanner(int id, Set<Position> observations) {
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public OverlapResult getOverlappingBeacons(final Scanner other) {
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for (final var direction : Direction.values()) {
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for (final var rotation : Rotation.values()) {
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final var transformation = new Transformation(direction, rotation);
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final var distances = observations().stream()
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.flatMap(a -> other.observations()
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.stream()
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.map(transformation::reorient)
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.map(a::minus))
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.collect(Collectors.toList());
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for (final var offset : distances) {
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final var intersection = other.observations()
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.stream()
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.map(transformation::reorient)
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.map(observation -> observation.plus(offset))
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.filter(observations()::contains)
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.collect(Collectors.toUnmodifiableSet());
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if (intersection.size() >= 12) {
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return new Overlap(offset, transformation, intersection);
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}
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}
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}
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}
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return new None();
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}
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}
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@Nested
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public class ScannerTest {
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@Test
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public final void testOverlapWithOrigin() {
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// given
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final var scanner0Observations = """
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404,-588,-901
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528,-643,409
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-838,591,734
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390,-675,-793
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-537,-823,-458
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-485,-357,347
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-345,-311,381
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-661,-816,-575
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-876,649,763
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-618,-824,-621
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553,345,-567
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474,580,667
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-447,-329,318
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-584,868,-557
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544,-627,-890
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564,392,-477
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455,729,728
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-892,524,684
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-689,845,-530
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423,-701,434
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7,-33,-71
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630,319,-379
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443,580,662
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-789,900,-551
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459,-707,401
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""";
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final var scanner1Observations = """
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686,422,578
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605,423,415
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515,917,-361
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-336,658,858
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95,138,22
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-476,619,847
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-340,-569,-846
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567,-361,727
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-460,603,-452
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669,-402,600
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729,430,532
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-500,-761,534
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-322,571,750
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-466,-666,-811
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-429,-592,574
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-355,545,-477
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703,-491,-529
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-328,-685,520
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413,935,-424
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-391,539,-444
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586,-435,557
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-364,-763,-893
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807,-499,-711
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755,-354,-619
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553,889,-390
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""";
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final var scanner0 = new Scanner(0,
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Arrays.stream(scanner0Observations.split("\n"))
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.map(Position::parse)
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.collect(Collectors.toUnmodifiableSet()));
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final var scanner1 = new Scanner(0,
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Arrays.stream(scanner1Observations.split("\n"))
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.map(Position::parse)
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.collect(Collectors.toUnmodifiableSet()));
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// when
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final var result = scanner0.getOverlappingBeacons(scanner1);
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// then
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assertTrue(result instanceof Overlap);
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final var overlap = (Overlap) result;
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assertEquals(12, overlap.overlappingBeacons().size());
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}
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@Test
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public final void testOverlapWithNonOrigin() {
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// given
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final var scanner1Observations = """
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686,422,578
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605,423,415
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515,917,-361
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-336,658,858
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95,138,22
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-476,619,847
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-340,-569,-846
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567,-361,727
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-460,603,-452
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669,-402,600
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729,430,532
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-500,-761,534
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-322,571,750
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-466,-666,-811
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-429,-592,574
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-355,545,-477
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703,-491,-529
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-328,-685,520
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413,935,-424
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-391,539,-444
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586,-435,557
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-364,-763,-893
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807,-499,-711
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755,-354,-619
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553,889,-390
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""";
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final var scanner4Observations = """
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727,592,562
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-293,-554,779
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441,611,-461
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-714,465,-776
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-743,427,-804
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-660,-479,-426
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832,-632,460
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927,-485,-438
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408,393,-506
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466,436,-512
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110,16,151
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-258,-428,682
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-393,719,612
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-211,-452,876
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808,-476,-593
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-575,615,604
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-485,667,467
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-680,325,-822
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-627,-443,-432
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872,-547,-609
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833,512,582
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807,604,487
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839,-516,451
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891,-625,532
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-652,-548,-490
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30,-46,-14
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""";
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final var scanner1 = new Scanner(0,
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Arrays.stream(scanner1Observations.split("\n"))
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.map(Position::parse)
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.collect(Collectors.toUnmodifiableSet()));
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final var scanner4 = new Scanner(0,
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Arrays.stream(scanner4Observations.split("\n"))
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.map(Position::parse)
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.collect(Collectors.toUnmodifiableSet()));
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// when
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final var result = scanner1.getOverlappingBeacons(scanner4);
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// then
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assertTrue(result instanceof Overlap);
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final var overlap = (Overlap) result;
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assertEquals(12, overlap.overlappingBeacons().size());
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}
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}
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@Test
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public final void part1() {
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final var scanners = getScanners();
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final var knownBeacons = new HashSet<Position>();
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final var origin = new Scanner(-1, knownBeacons);
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final var remaining = new ArrayList<>(scanners);
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while (!remaining.isEmpty()) {
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final var other = remaining.remove(0);
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if (knownBeacons.isEmpty()) {
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knownBeacons.addAll(other.observations());
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continue;
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}
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final var result = origin.getOverlappingBeacons(other);
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if (result instanceof final Overlap overlap) {
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knownBeacons.addAll(other.observations()
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.stream()
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.map(overlap.transformation()::reorient)
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.map(observation -> observation.plus(overlap.distance()))
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.collect(Collectors.toList()));
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} else {
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remaining.add(other);
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}
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}
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System.out.println("Part 1: " + knownBeacons.size());
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}
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@Test
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public final void part2() {
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final var scanners = getScanners();
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final var knownBeacons = new HashSet<Position>();
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final var origin = new Scanner(-1, knownBeacons);
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final var remaining = new ArrayList<>(scanners);
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final var distances = new HashSet<Position>();
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while (!remaining.isEmpty()) {
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final var other = remaining.remove(0);
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if (knownBeacons.isEmpty()) {
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knownBeacons.addAll(other.observations());
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continue;
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}
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final var result = origin.getOverlappingBeacons(other);
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if (result instanceof final Overlap overlap) {
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knownBeacons.addAll(other.observations()
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.stream()
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.map(overlap.transformation()::reorient)
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.map(observation -> observation.plus(overlap.distance()))
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.collect(Collectors.toList()));
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distances.add(overlap.distance());
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} else {
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remaining.add(other);
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}
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}
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int maxDistance = Integer.MIN_VALUE;
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for (final var x : distances) {
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for (final var y : distances) {
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final int distance = Math.abs(x.x() - y.x())
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+ Math.abs(x.y() - y.y())
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+ Math.abs(x.z() - y.z());
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maxDistance = Math.max(maxDistance, distance);
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}
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}
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System.out.println("Part 2: " + maxDistance);
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}
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}

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