fix binomial0 & add test

1 files changed, 21 insertions, 0 deletions

diff --git a/math/test/binomial0.cpp b/math/test/binomial0.cpp
new file mode 100644
index 0000000..d6c3a03
--- /dev/null
+++ b/math/test/binomial0.cpp
@@ -0,0 +1,21 @@
+constexpr ll mod = 1'000'000'007;
+
+#include "../shortModInv.cpp"
+#include "../binomial0.cpp"
+
+int main() {
+	precalc();
+	assert(calc_binom(5, -1) == 0);
+	assert(calc_binom(5, 0) == 1);
+	assert(calc_binom(5, 1) == 5);
+	assert(calc_binom(5, 2) == 10);
+	assert(calc_binom(5, 3) == 10);
+	assert(calc_binom(5, 4) == 5);
+	assert(calc_binom(5, 5) == 1);
+	assert(calc_binom(5, 6) == 0);
+	assert(calc_binom(0, 0) == 1);
+	assert(calc_binom(-1, 0) == 0);
+	assert(calc_binom(-1, -1) == 0);
+	assert(calc_binom(-1, -2) == 0);
+	assert(calc_binom(100'000, 50'000) == 149033233);
+}