1 files changed, 122 insertions, 0 deletions

diff --git a/2025/src/day08.cpp b/2025/src/day08.cpp
new file mode 100644
index 0000000..366d827
--- /dev/null
+++ b/2025/src/day08.cpp
@@ -0,0 +1,122 @@
+#include <cmath>
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <tuple>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+class UnionFind {
+public:
+        explicit UnionFind(size_t size)
+            : parent_(size)
+        {
+                for ( size_t i = 0; i != size; ++i ) {
+                        parent_[i] = i;
+                }
+        }
+
+        size_t find(size_t n)
+        {
+                if ( parent_[n] != n ) {
+                        parent_[n] = find(parent_[n]);
+                }
+                return parent_[n];
+        }
+
+        void unite(size_t a, size_t b)
+        {
+                a = find(a);
+                b = find(b);
+
+                parent_[b] = a;
+        }
+
+private:
+        vector<size_t> parent_;
+};
+
+using Pos = tuple<long, long, long>;
+
+vector<Pos>
+read_file(const filesystem::path& filename)
+{
+        ifstream file{ filename };
+
+        vector<Pos> list;
+
+        long x{};
+        long y{};
+        long z{};
+        char ch{};
+
+        while ( file >> x >> ch >> y >> ch >> z ) {
+                list.emplace_back(x, y, z);
+        }
+
+        return list;
+}
+
+double
+get_distance(const Pos& pos1, const Pos& pos2)
+{
+        const auto [x1, y1, z1] = pos1;
+        const auto [x2, y2, z2] = pos2;
+
+        return hypot(x1 - x2, y1 - y2, z1 - z2);
+}
+
+void
+part1(const vector<Pos>& list)
+{
+        using Dist = tuple<double, size_t, size_t>; // (Distanz, Von, Nach)
+
+        // Distanzen paarweise erfassen...
+        vector<Dist> dists;
+        for ( size_t i = 0; i != list.size(); ++i ) {
+                for ( size_t j = i + 1; j != list.size(); ++j ) {
+                        dists.emplace_back(get_distance(list[i], list[j]), i, j);
+                }
+        }
+
+        // ... und nach Distanz sortieren
+        ranges::sort(dists);
+
+        UnionFind unionFind(list.size());
+
+        // die kürzesten 1000 Elemente verbinden
+        for ( size_t i = 0; i != 1000; ++i ) {
+                const auto [dist, a, b] = dists[i];
+                unionFind.unite(a, b);
+        }
+
+        // die Längen der Verbindungen zählen
+        map<size_t, size_t> compSizes;
+        for ( size_t i = 0; i != list.size(); ++i ) {
+                compSizes[unionFind.find(i)]++;
+        }
+
+        // Größen finden
+        vector<size_t> sizes;
+        for ( const auto& [root, size]: compSizes ) {
+                sizes.emplace_back(size);
+        }
+
+        // Sortieren
+        ranges::sort(sizes, greater<>());
+
+        cout << "Part 1: " << sizes[0] * sizes[1] * sizes[2] << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+        auto data = read_file("data/day08.txt");
+        part1(data);
+}