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Day 14
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‎src/test/java/com/macasaet/Day14.java

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package com.macasaet;
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import org.junit.jupiter.api.Test;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.stream.StreamSupport;
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/**
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* --- Day 14: Regolith Reservoir ---
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* <a href="https://adventofcode.com/2022/day/14">https://adventofcode.com/2022/day/14</a>
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*/
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public class Day14 {
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public enum Cell {
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ROCK,
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SAND
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}
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record Coordinate(int verticalDepth, int horizontalOffset) {
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public static Coordinate parse(final String string) {
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final var components = string.split(",");
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final var verticalDepth = Integer.parseInt(components[1]);
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final var horizontalOffset = Integer.parseInt(components[0]);
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return new Coordinate(verticalDepth, horizontalOffset);
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}
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}
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public record Cave(Map<Integer, Map<Integer, Cell>> grid, int maxDepth, int minHorizontalOffset, int maxHorizontalOffset) {
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public int pourSandIntoAbyss() {
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int settledSand = 0;
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while(true) {
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var fallingSandCoordinate = new Coordinate(0, 500);
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while(true) {
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final var next = getNextCoordinate(fallingSandCoordinate, null);
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if(next != null) {
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fallingSandCoordinate = next;
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if(fallingSandCoordinate.verticalDepth() >= maxDepth()) {
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return settledSand;
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}
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} else {
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final var row = grid.computeIfAbsent(fallingSandCoordinate.verticalDepth(), key -> new HashMap<>());
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row.put(fallingSandCoordinate.horizontalOffset(), Cell.SAND);
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settledSand++;
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break;
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}
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}
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}
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}
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public int fillAperture() {
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int settledSand = 0;
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while(true) {
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var fallingSandCoordinate = new Coordinate(0, 500);
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while(true) {
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final var next = getNextCoordinate(fallingSandCoordinate, floorDepth());
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if(next != null) {
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fallingSandCoordinate = next;
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} else {
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final var secondRow = grid().computeIfAbsent(1, key -> new HashMap<>());
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if(secondRow.containsKey(499) && secondRow.containsKey(500) && secondRow.containsKey(501)) {
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return settledSand + 1;
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}
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final var row = grid.computeIfAbsent(fallingSandCoordinate.verticalDepth(), key -> new HashMap<>());
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row.put(fallingSandCoordinate.horizontalOffset(), Cell.SAND);
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settledSand++;
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break;
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}
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}
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}
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}
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int floorDepth() {
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return maxDepth() + 2;
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}
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Coordinate getNextCoordinate(final Coordinate start, Integer floorDepth) {
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final var x = start.verticalDepth();
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final var y = start.horizontalOffset();
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if(floorDepth != null && x + 1 >= floorDepth) {
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return null;
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}
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final var nextRow = grid().computeIfAbsent(x + 1, key -> new HashMap<>());
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if(!nextRow.containsKey(y)) {
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return new Coordinate(x + 1, y);
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} else if(!nextRow.containsKey(y - 1)) {
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return new Coordinate(x + 1, y - 1);
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} else if(!nextRow.containsKey(y + 1)) {
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return new Coordinate(x + 1, y + 1);
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}
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return null;
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}
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public static Cave parse(final Collection<? extends String> lines) {
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int maxDepth = 0;
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int maxHorizontalOffset = Integer.MIN_VALUE;
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int minHorizontalOffset = Integer.MAX_VALUE;
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final var grid = new HashMap<Integer, Map<Integer, Cell>>();
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for(final var line : lines) {
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final var rockPath = parseRockPaths(line);
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var last = rockPath.get(0);
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if(last.verticalDepth() > maxDepth) {
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maxDepth = last.verticalDepth();
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}
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if(last.horizontalOffset() < minHorizontalOffset) {
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minHorizontalOffset = last.horizontalOffset();
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}
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if(last.horizontalOffset() > maxHorizontalOffset) {
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maxHorizontalOffset = last.horizontalOffset();
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}
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for(int i = 1; i < rockPath.size(); i++) {
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final var current = rockPath.get(i);
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if(last.verticalDepth() == current.verticalDepth()) {
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// horizontal line
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int start;
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int end;
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if(last.horizontalOffset() < current.horizontalOffset()) {
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start = last.horizontalOffset();
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end = current.horizontalOffset();
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} else {
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start = current.horizontalOffset();
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end = last.horizontalOffset();
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}
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final var row = grid.computeIfAbsent(last.verticalDepth(), key -> new HashMap<>());
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for(int y = start; y <= end; y++) {
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row.put(y, Cell.ROCK);
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}
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} else {
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if(last.horizontalOffset() != current.horizontalOffset()) {
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throw new IllegalStateException("Line segments are not on the same vertical axis");
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}
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// vertical line
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int start;
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int end;
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if(last.verticalDepth() < current.verticalDepth()) {
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start = last.verticalDepth();
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end = current.verticalDepth();
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} else {
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start = current.verticalDepth();
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end = last.verticalDepth();
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}
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for(int x = start; x <= end; x++) {
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final var row = grid.computeIfAbsent(x, key -> new HashMap<>());
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row.put(last.horizontalOffset(), Cell.ROCK);
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}
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}
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if(current.verticalDepth() > maxDepth) {
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maxDepth = current.verticalDepth();
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}
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if(current.horizontalOffset() < minHorizontalOffset) {
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minHorizontalOffset = current.horizontalOffset();
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}
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if(current.horizontalOffset() > maxHorizontalOffset) {
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maxHorizontalOffset = current.horizontalOffset();
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}
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last = current;
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}
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}
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return new Cave(grid, maxDepth, minHorizontalOffset, maxHorizontalOffset);
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}
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static List<Coordinate> parseRockPaths(final String line) {
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return Arrays.stream(line.split(" -> ")).map(Coordinate::parse).toList();
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}
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@Override
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public String toString() {
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final var buffer = new StringBuilder();
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for(int i = 0; i <= floorDepth(); i++) {
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buffer.append(i).append(' ');
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final var row = grid.getOrDefault(i, Collections.emptyMap());
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for(int j = minHorizontalOffset(); j <= maxHorizontalOffset(); j++) {
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final var cell = row.get(j);
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final char marker = cell == null ? ' ' : Cell.ROCK.equals(cell) ? '#' : 'o';
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buffer.append(marker);
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}
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buffer.append('\n');
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}
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return buffer.toString();
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}
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}
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protected Cave getInput() {
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final var lines = StreamSupport.stream(new LineSpliterator("day-14.txt"), false)
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.toList();
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return Cave.parse(lines);
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}
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@Test
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public final void part1() {
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final var cave = getInput();
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final var result = cave.pourSandIntoAbyss();
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System.out.println("Part 1: " + result);
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}
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@Test
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public final void part2() {
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final var cave = getInput();
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final var result = cave.fillAperture();
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System.out.println("Part 2: " + result);
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}
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}

‎src/test/resources/sample/day-14.txt

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498,4 -> 498,6 -> 496,6
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503,4 -> 502,4 -> 502,9 -> 494,9

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