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pareroniapareronia
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AoC 2025 Day 8 - java - refactor
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‎src/main/java/AoC2025_08.java‎

Lines changed: 62 additions & 73 deletions
Original file line numberDiff line numberDiff line change
@@ -1,15 +1,12 @@
11
import static com.github.pareronia.aoc.IntegerSequence.Range.range;
22

33
import static java.util.Comparator.comparing;
4-
import static java.util.Comparator.reverseOrder;
5-
import static java.util.stream.Collectors.toMap;
64

75
import com.github.pareronia.aoc.StringOps;
86
import com.github.pareronia.aoc.geometry3d.Position3D;
97
import com.github.pareronia.aoc.solution.SolutionBase;
108

11-
import java.util.ArrayList;
12-
import java.util.Collections;
9+
import java.util.Arrays;
1310
import java.util.List;
1411

1512
@SuppressWarnings({"PMD.ClassNamingConventions", "PMD.NoPackage"})
@@ -29,39 +26,30 @@ public static AoC2025_08 createDebug() {
2926

3027
@Override
3128
protected Input parseInput(final List<String> inputs) {
32-
final List<Position3D> boxes =
33-
inputs.stream()
34-
.map(
35-
s -> {
36-
final String[] splits = s.split(",");
37-
return Position3D.of(
38-
Integer.parseInt(splits[0]),
39-
Integer.parseInt(splits[1]),
40-
Integer.parseInt(splits[2]));
41-
})
29+
final List<Box> boxes =
30+
range(inputs.size()).stream().map(i -> Box.fromInput(i, inputs.get(i))).toList();
31+
final List<Pair> pairs =
32+
range(boxes.size()).stream()
33+
.flatMap(
34+
i ->
35+
range(i + 1, boxes.size(), 1).stream()
36+
.map(j -> Pair.of(boxes.get(i), boxes.get(j))))
37+
.sorted(comparing(Pair::distance))
4238
.toList();
43-
final List<Pair> pairs = new ArrayList<>();
44-
for (int i = 0; i < boxes.size(); i++) {
45-
for (int j = i + 1; j < boxes.size(); j++) {
46-
pairs.add(new Pair(i, j, boxes.get(i).squaredDistance(boxes.get(j))));
47-
}
48-
}
49-
Collections.sort(pairs, comparing(Pair::distance));
5039
return new Input(boxes, pairs);
5140
}
5241

42+
@SuppressWarnings("PMD.LawOfDemeter")
5343
private long solve1(final Input input, final int size) {
5444
final DSU dsu = new DSU(input.boxes().size());
55-
input.pairs().stream().limit(size).forEach(pair -> dsu.unify(pair.first(), pair.second()));
56-
return range(input.boxes().size()).stream()
57-
.collect(toMap(i -> i, dsu::componentSize))
58-
.values()
59-
.stream()
60-
.distinct()
61-
.sorted(reverseOrder())
62-
.limit(3)
45+
input.pairs().stream()
46+
.limit(size)
47+
.forEach(pair -> dsu.unify(pair.first().idx(), pair.second().idx()));
48+
return Arrays.stream(dsu.sz)
49+
.sorted()
50+
.skip(dsu.sz.length - 3)
6351
.reduce((acc, sz) -> acc * sz)
64-
.get();
52+
.getAsInt();
6553
}
6654

6755
@Override
@@ -70,16 +58,20 @@ public Long solvePart1(final Input input) {
7058
}
7159

7260
@Override
61+
@SuppressWarnings("PMD.LawOfDemeter")
7362
public Long solvePart2(final Input input) {
7463
final DSU dsu = new DSU(input.boxes().size());
75-
for (final Pair pair : input.pairs()) {
76-
dsu.unify(pair.first(), pair.second());
77-
if (dsu.components() == 1 && dsu.componentSize(0) == input.boxes().size()) {
78-
return ((long) input.boxes().get(pair.first()).getX())
79-
* input.boxes().get(pair.second()).getX();
80-
}
81-
}
82-
throw new IllegalStateException("Unsolvable");
64+
return input.pairs().stream()
65+
.mapToLong(
66+
pair -> {
67+
dsu.unify(pair.first().idx(), pair.second().idx());
68+
return ((long) pair.first().position().getX())
69+
* pair.second().position().getX();
70+
})
71+
.dropWhile(
72+
x -> dsu.numComponents != 1 || dsu.sz[dsu.find(0)] != input.boxes().size())
73+
.findFirst()
74+
.orElseThrow();
8375
}
8476

8577
@Override
@@ -118,9 +110,27 @@ public static void main(final String[] args) throws Exception {
118110
425,690,689
119111
""";
120112

121-
record Pair(int first, int second, long distance) {}
113+
record Box(int idx, Position3D position) {
114+
115+
public static Box fromInput(final int idx, final String input) {
116+
final String[] splits = input.split(",");
117+
return new Box(
118+
idx,
119+
Position3D.of(
120+
Integer.parseInt(splits[0]),
121+
Integer.parseInt(splits[1]),
122+
Integer.parseInt(splits[2])));
123+
}
124+
}
125+
126+
record Pair(Box first, Box second, long distance) {
127+
128+
public static Pair of(final Box first, final Box second) {
129+
return new Pair(first, second, first.position().squaredDistance(second.position()));
130+
}
131+
}
122132

123-
record Input(List<Position3D> boxes, List<Pair> pairs) {}
133+
record Input(List<Box> boxes, List<Pair> pairs) {}
124134

125135
private static class DSU {
126136

@@ -140,48 +150,27 @@ public DSU(final int size) {
140150
}
141151

142152
public int find(final int p) {
143-
int target = p;
144-
int root = target;
153+
int root = p;
145154
while (root != id[root]) {
146155
root = id[root];
147156
}
148-
149-
while (target != root) {
150-
final int next = id[target];
151-
id[target] = root;
152-
target = next;
153-
}
154-
155157
return root;
156158
}
157159

158-
public int componentSize(final int p) {
159-
return sz[find(p)];
160-
}
161-
162-
public int components() {
163-
return numComponents;
164-
}
165-
166-
@SuppressWarnings("PMD.OnlyOneReturn")
167-
public int unify(final int p, final int q) {
168-
if (find(p) == find(q)) {
169-
return 0;
170-
}
160+
public void unify(final int p, final int q) {
171161
final int root1 = find(p);
172162
final int root2 = find(q);
173-
if (sz[root1] < sz[root2]) {
174-
sz[root2] += sz[root1];
175-
id[root1] = root2;
176-
sz[root1] = 0;
177-
numComponents--;
178-
return root2;
179-
} else {
180-
sz[root1] += sz[root2];
181-
id[root2] = root1;
182-
sz[root2] = 0;
163+
if (root1 != root2) {
164+
if (sz[root1] < sz[root2]) {
165+
sz[root2] += sz[root1];
166+
id[root1] = root2;
167+
sz[root1] = 0;
168+
} else {
169+
sz[root1] += sz[root2];
170+
id[root2] = root1;
171+
sz[root2] = 0;
172+
}
183173
numComponents--;
184-
return root1;
185174
}
186175
}
187176
}

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