From ea880ec267d96ee136a29ae7e18847ec839ad016 Mon Sep 17 00:00:00 2001
From: Vladimir Chalupecky <vladimir.chalupecky@gmail.com>
Date: Wed, 19 Apr 2017 20:30:22 +0200
Subject: [PATCH] stat/combin: avoid overflow in Binomial

Fixes #174
---
 combin/combin.go | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/combin/combin.go b/combin/combin.go
index ae1b4a0..4dba68f 100644
--- a/combin/combin.go
+++ b/combin/combin.go
@@ -35,15 +35,11 @@ func Binomial(n, k int) int {
 	if k > n/2 {
 		k = n - k
 	}
-	kfact := 1
-	for i := 2; i <= k; i++ {
-		kfact *= i
+	b := 1
+	for i := 1; i <= k; i++ {
+		b = (n - k + i) * b / i
 	}
-	num := 1
-	for i := n; i > n-k; i-- {
-		num *= i
-	}
-	return num / kfact
+	return b
 }
 
 // GeneralizedBinomial returns the generalized binomial coefficient of (n, k),