1 files changed, 91 insertions, 0 deletions
diff --git a/test/graph/kruskal.cpp b/test/graph/kruskal.cpp
new file mode 100644
index 0000000..f6245b9
--- /dev/null
+++ b/test/graph/kruskal.cpp
@@ -0,0 +1,91 @@
+#include "../util.h"
+#include <datastructures/unionFind.cpp>
+
+struct edge {
+	int from, to;
+	ll cost;
+	bool operator<(const edge& o) const {
+		return cost > o.cost;
+	}
+};
+ll kruskal(vector<edge>& edges, int n) {
+	init(n);
+	#define Edge edge
+	#include <graph/kruskal.cpp>
+	#undef Edge
+	return cost;
+}
+
+ll prim(vector<edge>& edges, int n) {
+	vector<vector<pair<ll, int>>> adj(n);
+	for (auto [a, b, d] : edges) {
+		adj[a].emplace_back(d, b);
+		adj[b].emplace_back(d, a);
+	}
+	priority_queue<pair<ll, int>> todo;
+	vector<bool> seen(n);
+	ll res = 0;
+	for (ll i = 0; i < n; i++) {
+		if (seen[i]) continue;
+		todo.push({0, i});
+		while (!todo.empty()) {
+			auto [d, c] = todo.top();
+			todo.pop();
+			if (seen[c]) continue;
+			seen[c] = true;
+			res += d;
+			for (auto e : adj[c]) {
+				todo.push(e);
+			}
+		}
+	}
+	return res;
+}
+
+void stress_test() {
+	ll queries = 0;
+	for (int tries = 0; tries < 100'000; tries++) {
+		int n = Random::integer<int>(2, 30);
+		int m = Random::integer<int>(0, max<int>(n, min<int>(500, n*(n-1) / 2 + 1)));
+
+
+		Graph<NoData> g(n);
+		g.erdosRenyi(m);
+		vector<edge> edges;
+		g.forEdges([&](int a, int b){
+			ll w = Random::integer<ll>(-1'000'000'000ll, 1'000'000'000ll);
+			edges.push_back({a, b, w});
+		});
+
+		ll got = kruskal(edges, n);
+		ll expected = prim(edges, n);
+
+		if (got != expected) cerr << "got: " << got << ", expected: " << expected << FAIL;
+		queries += n;
+	}
+	cerr << "tested random queries: " << queries << endl;
+}
+
+constexpr int N = 500'000;
+constexpr int M = 3'000'000;
+void performance_test() {
+	timer t;
+	Graph<NoData> g(N);
+	g.erdosRenyi(M);
+	vector<edge> edges;
+	g.forEdges([&](int a, int b){
+		ll w = Random::integer<ll>(-1'000'000'000ll, 1'000'000'000ll);
+		edges.push_back({a, b, w});
+	});
+
+	t.start();
+	hash_t hash = kruskal(edges, N);
+	t.stop();
+	if (t.time > 1000) cerr << "too slow: " << t.time << FAIL;
+	cerr << "tested performance: " << t.time << "ms (hash: " << hash << ")" << endl;
+}
+
+int main() {
+	stress_test();
+	performance_test();
+}