1 files changed, 21 insertions, 0 deletions
diff --git a/test/math/kthperm_permIndex.cpp b/test/math/kthperm_permIndex.cpp
new file mode 100644
index 0000000..d84524e
--- /dev/null
+++ b/test/math/kthperm_permIndex.cpp
@@ -0,0 +1,21 @@
+#include "../util.h"
+#include <datastructures/pbds.cpp>
+#include <math/kthperm.cpp>
+#include <math/permIndex.cpp>
+
+void stress_test() {
+	ll queries = 0;
+	for (ll i = 0; i < 10'000; i++) {
+		ll n = Random::integer<ll>(20, 1000);
+		ll expected = Random::integer<ll>(0, 1'000'000'000'000'000'000);
+		ll got = permIndex(kthperm(n, expected));
+		if (got != expected) cerr << "got: " << got << ", expected: " << expected << FAIL;
+		queries += n;
+	}
+	cerr << "tested queries: " << queries << endl;
+}
+
+int main() {
+	stress_test();
+}
+