diff options
| author | Weixie Cui <cuiweixie@gmail.com> | 2026-04-06 10:36:44 +0000 |
|---|---|---|
| committer | Gopher Robot <gobot@golang.org> | 2026-04-07 14:58:27 -0700 |
| commit | e3b3216242691ab0e02164458bda98346ce36adf (patch) | |
| tree | aa95dd0273ddac3968928443fe3301e075a1050e | |
| parent | 6f662188c2e2640712af74a01f589ee31ba0282f (diff) | |
| download | go-e3b3216242691ab0e02164458bda98346ce36adf.tar.xz | |
math/big: Binomial should return 0 if k < 0
Fixes #78541
Change-Id: I73ba10b6d34f9f189b5bdd356d6325d5a4a6985f
GitHub-Last-Rev: 0594d99f55c51f2f164d17a61c4eb1b2bbb8462e
GitHub-Pull-Request: golang/go#78542
Reviewed-on: https://go-review.googlesource.com/c/go/+/763000
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Neal Patel <nealpatel@google.com>
| -rw-r--r-- | src/math/big/int.go | 2 | ||||
| -rw-r--r-- | src/math/big/int_test.go | 1 |
2 files changed, 2 insertions, 1 deletions
diff --git a/src/math/big/int.go b/src/math/big/int.go index 8eb0db6c58..3c6f0d4028 100644 --- a/src/math/big/int.go +++ b/src/math/big/int.go @@ -227,7 +227,7 @@ func (z *Int) MulRange(a, b int64) *Int { // Binomial sets z to the binomial coefficient C(n, k) and returns z. func (z *Int) Binomial(n, k int64) *Int { - if k > n { + if k > n || k < 0 { return z.SetInt64(0) } // reduce the number of multiplications by reducing k diff --git a/src/math/big/int_test.go b/src/math/big/int_test.go index eb5c177be0..f6865d1ed9 100644 --- a/src/math/big/int_test.go +++ b/src/math/big/int_test.go @@ -255,6 +255,7 @@ func TestBinomial(t *testing.T) { {100, 90, "17310309456440"}, {1000, 10, "263409560461970212832400"}, {1000, 990, "263409560461970212832400"}, + {5, -1, "0"}, } { if got := z.Binomial(test.n, test.k).String(); got != test.want { t.Errorf("Binomial(%d, %d) = %s; want %s", test.n, test.k, got, test.want) |