1 files changed, 77 insertions, 0 deletions
diff --git a/test/graph/centroid.cpp b/test/graph/centroid.cpp
new file mode 100644
index 0000000..41d9d0f
--- /dev/null
+++ b/test/graph/centroid.cpp
@@ -0,0 +1,77 @@
+#include "../util.h"
+vector<vector<int>> adj;
+#include <graph/centroid.cpp>
+
+int subtreeSize(int c, int p) {
+	int res = 1;
+	for (int x : adj[c]) {
+		if (x == p) continue;
+		res += subtreeSize(x, c);
+	}
+	return res;
+}
+
+vector<int> naive() {
+	vector<int> res;
+	for (int i = 0; i < sz(adj); i++) {
+		bool isCentroid = true;
+		for (int j : adj[i]) isCentroid &= 2*subtreeSize(j, i) <= sz(adj);
+		if (isCentroid) res.push_back(i);
+	}
+	return res;
+}
+
+void stress_test() {
+	ll queries = 0;
+	for (int tries = 0; tries < 100'000; tries++) {
+		int n = Random::integer<int>(1, 50);
+		Graph<NoData> g(n);
+		g.tree();
+
+		adj.assign(n, {});
+		g.forEdges([&](int a, int b){
+			adj[a].push_back(b);
+			adj[b].push_back(a);
+		});
+		
+		auto expected = naive();
+		sort(all(expected));
+
+		for (int i = 0; i < n; i++) {
+			auto [a, b] = find_centroid(i);
+			vector<int> got;
+			if (a >= 0) got.push_back(a);
+			if (b >= 0) got.push_back(b);
+			sort(all(got));
+
+			if (got != expected) cerr << "error" << FAIL;
+		}
+		queries += n;
+	}
+	cerr << "tested random queries: " << queries << endl;
+}
+
+constexpr int N = 2'000'000;
+void performance_test() {
+	timer t;
+	Graph<NoData> g(N);
+	g.tree();
+
+	adj.assign(N, {});
+	g.forEdges([&](int a, int b){
+		adj[a].push_back(b);
+		adj[b].push_back(a);
+	});
+
+	t.start();	
+	auto [gotA, gotB] = find_centroid();
+	t.stop();
+	hash_t hash = gotA + gotB;
+	if (t.time > 500) cerr << "too slow: " << t.time << FAIL;
+	cerr << "tested performance: " << t.time << "ms (hash: " << hash << ")" << endl;
+}
+
+int main() {
+	stress_test();
+	performance_test();
+}