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FlashkyFlashky
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Solve day 24 puzzle part 1
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6 files changed

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‎pom.xml‎

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<artifactId>commons-math3</artifactId>
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<version>3.6.1</version>
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</dependency>
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<dependency>
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<groupId>org.apache.commons</groupId>
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<artifactId>commons-geometry-euclidean</artifactId>
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<version>1.0</version>
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</dependency>
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</dependencies>
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‎src/main/java/com/adventofcode/flashk/day24/Hailstone.java‎

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package com.adventofcode.flashk.day24;
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import lombok.Getter;
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import org.apache.commons.geometry.euclidean.threed.Vector3D;
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import org.apache.commons.geometry.euclidean.threed.line.Line3D;
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import org.apache.commons.geometry.euclidean.threed.line.Lines3D;
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import org.apache.commons.lang3.StringUtils;
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import org.apache.commons.numbers.core.Precision;
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public class Hailstone {
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private Vector3D position;
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private Vector3D speed;
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@Getter
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private Line3D trajectory;
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public Hailstone(String input, boolean isPartOne) {
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String[] inputParts = input.split("@");
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String[] posCoords = StringUtils.deleteWhitespace(inputParts[0]).split(",");
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String[] speedCoords = StringUtils.deleteWhitespace(inputParts[1]).split(",");
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if(isPartOne) {
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posCoords[2] = "0";
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speedCoords[2] = "0";
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}
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position = createVector3D(posCoords);
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speed = createVector3D(speedCoords);
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//Precision.DoubleEquivalence equivalence = Precision.doubleEquivalenceOfEpsilon(1e-6);
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Precision.DoubleEquivalence equivalence = Precision.doubleEquivalenceOfEpsilon(1e-10);
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trajectory = Lines3D.fromPointAndDirection(position, speed, equivalence);
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}
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public boolean intersectsInFuture(Hailstone other, long min, long max) {
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Vector3D intersection = trajectory.intersection(other.trajectory);
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// Parallel line
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if(intersection == null) {
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System.out.println("Hailstones's paths are parallel; they never intersect.");
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return false;
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}
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// Check intersection in time
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boolean isInFutureA = isInFuture(intersection);
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boolean isInFutureB = other.isInFuture(intersection);
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if(!isInFutureA && !isInFutureB) {
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System.out.println("Hailstones' paths crossed in the past for both hailstones.");
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return false;
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} else if(!isInFutureA) {
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System.out.println("Hailstones' paths crossed in the past for hailstone A.");
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return false;
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} else if(!isInFutureB) {
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System.out.println("Hailstones' paths crossed in the past for hailstone B.");
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return false;
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}
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boolean isInArea = isInArea(intersection, min, max);
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if(isInArea) {
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System.out.println("Hailstones' paths will cross inside the test area (at x="+intersection.getX()+", y="+intersection.getY()+").");
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} else {
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System.out.println("Hailstones' paths will cross outside the test area (at x="+intersection.getX()+", y="+intersection.getY()+").");
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}
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return isInArea;
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}
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private Vector3D createVector3D(String[] coords) {
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return Vector3D.of(Double.valueOf(coords[0]), Double.valueOf(coords[1]), Double.valueOf(coords[2]));
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}
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private boolean isInFuture(Vector3D intersection) {
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double deltaX = intersection.getX() - position.getX();
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if((deltaX > 0 && speed.getX() < 0) || (deltaX < 0 && speed.getX() > 0)){
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return false;
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}
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double deltaY = intersection.getY() - position.getY();
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if((deltaY > 0 && speed.getY() < 0) || (deltaY < 0 && speed.getY() > 0)){
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return false;
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}
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double deltaZ = intersection.getZ() - position.getZ();
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if((deltaZ > 0 && speed.getZ() < 0) || (deltaZ < 0 && speed.getZ() > 0)){
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return false;
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}
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return true;
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}
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private boolean isInArea(Vector3D intersection, long min, long max){
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return intersection.getX() >= min &&
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intersection.getX() <= max &&
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intersection.getY() >= min &&
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intersection.getY() <= max;
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}
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public boolean samePosition(Hailstone other) {
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return position.equals(other.position);
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}
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}

‎src/main/java/com/adventofcode/flashk/day24/HailstoneRefactor.java‎

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package com.adventofcode.flashk.day24;
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import org.apache.commons.geometry.euclidean.threed.Vector3D;
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import org.apache.commons.lang3.StringUtils;
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import org.apache.commons.math3.stat.regression.SimpleRegression;
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public class HailstoneRefactor {
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private Vector3D position;
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private Vector3D speed;
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private double slope; // m
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private double intercept; // b
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public HailstoneRefactor(String input, boolean isPartOne) {
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String[] inputParts = input.split("@");
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String[] posCoords = StringUtils.deleteWhitespace(inputParts[0]).split(",");
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String[] speedCoords = StringUtils.deleteWhitespace(inputParts[1]).split(",");
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if(isPartOne) {
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posCoords[2] = "0";
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speedCoords[2] = "0";
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}
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position = createVector3D(posCoords);
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speed = createVector3D(speedCoords);
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// Initialize slope and intercept
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Vector3D position2 = position.add(speed);
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SimpleRegression simpleRegression = new SimpleRegression();
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simpleRegression.addData(position.getX(), position.getY());
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simpleRegression.addData(position2.getX(), position2.getY());
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slope = simpleRegression.getSlope();
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intercept = simpleRegression.getIntercept();
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}
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public boolean intersectsInFuture(HailstoneRefactor other, long min, long max) {
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// Parallel trajectories
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if(slope == other.slope) {
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System.out.println("Hailstones's paths are parallel; they never intersect.");
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return false;
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}
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// Calculate intersection
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double intersectX = (other.intercept - intercept) / (slope - other.slope);
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double intersectY = slope * intersectX + intercept;
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Vector3D intersection = Vector3D.of(intersectX, intersectY, 0);
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boolean isInFutureA = isInFuture(intersection);
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boolean isInFutureB = other.isInFuture(intersection);
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if(!isInFutureA && !isInFutureB) {
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System.out.println("Hailstones' paths crossed in the past for both hailstones.");
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return false;
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} else if(!isInFutureA) {
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System.out.println("Hailstones' paths crossed in the past for hailstone A.");
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return false;
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} else if(!isInFutureB) {
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System.out.println("Hailstones' paths crossed in the past for hailstone B.");
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return false;
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}
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boolean isInArea = isInArea(intersection, min, max);
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if(isInArea) {
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System.out.println("Hailstones' paths will cross inside the test area (at x="+intersection.getX()+", y="+intersection.getY()+").");
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} else {
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System.out.println("Hailstones' paths will cross outside the test area (at x="+intersection.getX()+", y="+intersection.getY()+").");
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}
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return isInArea;
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}
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private Vector3D createVector3D(String[] coords) {
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return Vector3D.of(Double.valueOf(coords[0]), Double.valueOf(coords[1]), Double.valueOf(coords[2]));
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}
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private boolean isInFuture(Vector3D intersection) {
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double deltaX = intersection.getX() - position.getX();
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if((deltaX > 0 && speed.getX() < 0) || (deltaX < 0 && speed.getX() > 0)){
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return false;
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}
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double deltaY = intersection.getY() - position.getY();
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if((deltaY > 0 && speed.getY() < 0) || (deltaY < 0 && speed.getY() > 0)){
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return false;
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}
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double deltaZ = intersection.getZ() - position.getZ();
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if((deltaZ > 0 && speed.getZ() < 0) || (deltaZ < 0 && speed.getZ() > 0)){
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return false;
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}
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return true;
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}
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private boolean isInArea(Vector3D intersection, long min, long max){
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return intersection.getX() >= min &&
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intersection.getX() <= max &&
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intersection.getY() >= min &&
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intersection.getY() <= max;
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}
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}

‎src/main/java/com/adventofcode/flashk/day24/NeverTellMeTheOdds.java‎

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package com.adventofcode.flashk.day24;
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import java.util.ArrayList;
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import java.util.Iterator;
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import java.util.List;
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public class NeverTellMeTheOdds {
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private List<HailstoneRefactor> hailstones;
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public NeverTellMeTheOdds(List<String> inputs, boolean isPartOne) {
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if(isPartOne) {
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hailstones = inputs.stream().map(s -> new HailstoneRefactor(s, true)).toList();
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} else {
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hailstones = inputs.stream().map(s -> new HailstoneRefactor(s, false)).toList();
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}
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int a = 3;
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}
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public long solveA(long min, long max) {
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// Compare all hailstones combinations
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long result = 0;
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List<HailstoneRefactor> hailstonesCopy = new ArrayList<>(hailstones);
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while(!hailstonesCopy.isEmpty()) {
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Iterator<HailstoneRefactor> hailstoneIterator = hailstonesCopy.iterator();
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HailstoneRefactor hailstoneA = hailstoneIterator.next();
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while(hailstoneIterator.hasNext()) {
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HailstoneRefactor hailstoneB = hailstoneIterator.next();
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if(hailstoneA.intersectsInFuture(hailstoneB, min, max)) {
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result++;
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}
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}
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hailstonesCopy.remove(0);
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}
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return result;
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}
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}

‎src/test/java/com/adventofcode/flashk/day24/Day24Test.java‎

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import com.adventofcode.flashk.common.test.utils.Timer;
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import com.adventofcode.flashk.common.test.utils.Input;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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@DisplayName(TestDisplayName.DAY_24)
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@TestMethodOrder(OrderAnnotation.class)
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@Disabled // TODO Remove comment when implemented
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public class Day24Test extends PuzzleTest {
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private final static String INPUT_FOLDER = TestFolder.DAY_24;
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// Read input file
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List<String> inputs = Input.readStringLines(INPUT_FOLDER, TestFilename.INPUT_FILE_SAMPLE);
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NeverTellMeTheOdds neverTellMeTheOdds = new NeverTellMeTheOdds(inputs, true);
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long result = neverTellMeTheOdds.solveA(7, 27);
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assertEquals(2, result);
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}
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@Test
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// Read input file
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List<String> inputs = Input.readStringLines(INPUT_FOLDER, TestFilename.INPUT_FILE);
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NeverTellMeTheOdds neverTellMeTheOdds = new NeverTellMeTheOdds(inputs, true);
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long result = neverTellMeTheOdds.solveA(200000000000000L, 400000000000000L);
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//System.out.println("R: "+result);
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assertEquals(17244, result);
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// Con el algoritmo de Hailstone:
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// 683 -> That's not the right answer; your answer is too low.
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// Con el algoritmo de HailstoneRefactor:
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// 17244 -> OK
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}
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‎src/test/resources/inputs‎

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