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AoC 2025 Day 8 - java
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‎README.md‎

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| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
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| ---| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
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| python3 | [✓](src/main/python/AoC2025_01.py) | [✓](src/main/python/AoC2025_02.py) | [✓](src/main/python/AoC2025_03.py) | [✓](src/main/python/AoC2025_04.py) | [✓](src/main/python/AoC2025_05.py) | [✓](src/main/python/AoC2025_06.py) | [✓](src/main/python/AoC2025_07.py) | [✓](src/main/python/AoC2025_08.py) | | | | |
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| java | [✓](src/main/java/AoC2025_01.java) | [✓](src/main/java/AoC2025_02.java) | [✓](src/main/java/AoC2025_03.java) | [✓](src/main/java/AoC2025_04.java) | [✓](src/main/java/AoC2025_05.java) | [✓](src/main/java/AoC2025_06.java) | [✓](src/main/java/AoC2025_07.java) | | | | | |
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| java | [✓](src/main/java/AoC2025_01.java) | [✓](src/main/java/AoC2025_02.java) | [✓](src/main/java/AoC2025_03.java) | [✓](src/main/java/AoC2025_04.java) | [✓](src/main/java/AoC2025_05.java) | [✓](src/main/java/AoC2025_06.java) | [✓](src/main/java/AoC2025_07.java) | [✓](src/main/java/AoC2025_08.java) | | | | |
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| bash | [✓](src/main/bash/AoC2025_01.sh) | [✓](src/main/bash/AoC2025_02.sh) | [✓](src/main/bash/AoC2025_03.sh) | [✓](src/main/bash/AoC2025_04.sh) | [✓](src/main/bash/AoC2025_05.sh) | [✓](src/main/bash/AoC2025_06.sh) | [✓](src/main/bash/AoC2025_07.sh) | | | | | |
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<!-- @END:ImplementationsTable:2025@ -->
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‎src/main/java/AoC2025_08.java‎

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import static com.github.pareronia.aoc.IntegerSequence.Range.range;
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import static java.util.Comparator.comparing;
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import static java.util.Comparator.reverseOrder;
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import static java.util.stream.Collectors.toMap;
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import com.github.pareronia.aoc.StringOps;
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import com.github.pareronia.aoc.geometry3d.Position3D;
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import com.github.pareronia.aoc.solution.SolutionBase;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.List;
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@SuppressWarnings({"PMD.ClassNamingConventions", "PMD.NoPackage"})
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public final class AoC2025_08 extends SolutionBase<AoC2025_08.Input, Long, Long> {
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private AoC2025_08(final boolean debug) {
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super(debug);
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}
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public static AoC2025_08 create() {
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return new AoC2025_08(false);
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}
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public static AoC2025_08 createDebug() {
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return new AoC2025_08(true);
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}
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@Override
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protected Input parseInput(final List<String> inputs) {
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final List<Position3D> boxes =
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inputs.stream()
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.map(
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s -> {
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final String[] splits = s.split(",");
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return Position3D.of(
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Integer.parseInt(splits[0]),
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Integer.parseInt(splits[1]),
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Integer.parseInt(splits[2]));
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})
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.toList();
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final List<Pair> pairs = new ArrayList<>();
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for (int i = 0; i < boxes.size(); i++) {
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for (int j = i + 1; j < boxes.size(); j++) {
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pairs.add(new Pair(i, j, boxes.get(i).squaredDistance(boxes.get(j))));
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}
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}
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Collections.sort(pairs, comparing(Pair::distance));
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return new Input(boxes, pairs);
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}
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private long solve1(final Input input, final int size) {
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final DSU dsu = new DSU(input.boxes().size());
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input.pairs().stream().limit(size).forEach(pair -> dsu.unify(pair.first(), pair.second()));
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return range(input.boxes().size()).stream()
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.collect(toMap(i -> i, dsu::componentSize))
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.values()
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.stream()
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.distinct()
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.sorted(reverseOrder())
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.limit(3)
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.reduce((acc, sz) -> acc * sz)
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.get();
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}
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@Override
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public Long solvePart1(final Input input) {
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return this.solve1(input, 1000);
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}
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@Override
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public Long solvePart2(final Input input) {
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final DSU dsu = new DSU(input.boxes().size());
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for (final Pair pair : input.pairs()) {
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dsu.unify(pair.first(), pair.second());
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if (dsu.components() == 1 && dsu.componentSize(0) == input.boxes().size()) {
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return ((long) input.boxes().get(pair.first()).getX())
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* input.boxes().get(pair.second()).getX();
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}
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}
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throw new IllegalStateException("Unsolvable");
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}
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@Override
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protected void samples() {
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final AoC2025_08 test = createDebug();
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final Input input = test.parseInput(StringOps.splitLines(TEST));
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assert test.solve1(input, 10) == 40;
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assert test.solvePart2(input) == 25_272;
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}
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public static void main(final String[] args) throws Exception {
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create().run();
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}
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private static final String TEST =
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"""
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162,817,812
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57,618,57
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906,360,560
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592,479,940
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352,342,300
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466,668,158
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542,29,236
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431,825,988
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739,650,466
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52,470,668
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216,146,977
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819,987,18
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117,168,530
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805,96,715
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346,949,466
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970,615,88
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941,993,340
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862,61,35
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984,92,344
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425,690,689
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""";
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record Pair(int first, int second, long distance) {}
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record Input(List<Position3D> boxes, List<Pair> pairs) {}
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private static class DSU {
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private final int[] sz;
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private final int[] id;
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private int numComponents;
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public DSU(final int size) {
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this.numComponents = size;
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sz = new int[size];
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id = new int[size];
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for (int i = 0; i < size; i++) {
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id[i] = i;
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sz[i] = 1;
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}
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}
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public int find(final int p) {
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int target = p;
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int root = target;
145+
while (root != id[root]) {
146+
root = id[root];
147+
}
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149+
while (target != root) {
150+
final int next = id[target];
151+
id[target] = root;
152+
target = next;
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}
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155+
return root;
156+
}
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158+
public int componentSize(final int p) {
159+
return sz[find(p)];
160+
}
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public int components() {
163+
return numComponents;
164+
}
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166+
@SuppressWarnings("PMD.OnlyOneReturn")
167+
public int unify(final int p, final int q) {
168+
if (find(p) == find(q)) {
169+
return 0;
170+
}
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final int root1 = find(p);
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final int root2 = find(q);
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if (sz[root1] < sz[root2]) {
174+
sz[root2] += sz[root1];
175+
id[root1] = root2;
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sz[root1] = 0;
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numComponents--;
178+
return root2;
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} else {
180+
sz[root1] += sz[root2];
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id[root2] = root1;
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sz[root2] = 0;
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numComponents--;
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return root1;
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}
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}
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}
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}

‎src/main/java/com/github/pareronia/aoc/geometry3d/Position3D.java‎

Lines changed: 24 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -7,47 +7,53 @@ public class Position3D extends Point3D {
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public Position3D(final int x, final int y, final int z) {
88
super(x, y, z);
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}
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public static Position3D of(final int x, final int y, final int z) {
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return new Position3D(x, y, z);
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}
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public Position3D translate(final Vector3D vector) {
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return translate(vector, 1);
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}
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public Position3D translate(final Vector3D vector, final int amplitude) {
2020
return new Position3D(
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this.getX() + amplitude * vector.getX(),
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this.getY() + amplitude * vector.getY(),
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this.getZ() + amplitude * vector.getZ());
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}
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public double distance(final Position3D other) {
27-
return Math.sqrt(
28-
(other.getX() - this.getX()) * (other.getX() - this.getX()) +
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(other.getY() - this.getY()) * (other.getY() - this.getY()) +
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(other.getZ() - this.getZ()) * (other.getZ() - this.getZ())
31-
);
27+
return Math.sqrt(this.squaredDistance(other));
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}
33-
29+
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public long squaredDistance(final Position3D other) {
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final long dx = other.getX() - this.getX();
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final long dy = other.getY() - this.getY();
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final long dz = other.getZ() - this.getZ();
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return dx * dx + dy * dy + dz * dz;
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}
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3437
public Integer manhattanDistance(final Position3D from) {
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return Math.abs(this.getX() - from.getX())
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+ Math.abs(this.getY() - from.getY())
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+ Math.abs(this.getZ() - from.getZ());
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}
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4043
public Stream<Position3D> capitalNeighbours() {
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return Direction3D.CAPITAL.stream()
42-
.map(Direction3D::getValue)
43-
.map(this::translate);
44+
return Direction3D.CAPITAL.stream().map(Direction3D::getValue).map(this::translate);
4445
}
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46+
4647
@Override
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public String toString() {
48-
final StringBuilder builder = new StringBuilder();
49-
builder.append("Position3D(x=").append(getX()).append(", y=")
50-
.append(getY()).append(", z=").append(getZ()).append(")");
49+
final StringBuilder builder = new StringBuilder(50);
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builder.append("Position3D(x=")
51+
.append(getX())
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.append(", y=")
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.append(getY())
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.append(", z=")
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.append(getZ())
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.append(')');
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return builder.toString();
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}
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}

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