From 169a0ee704fd58c52c2d7c8a2561f0ddd3a892b9 Mon Sep 17 00:00:00 2001
From: codistmonk <codistmonk@7cbf5e2b-b55d-4b93-acdd-c0d7b961df51>
Date: Thu, 29 Mar 2012 15:48:40 +0000
Subject: [PATCH] [Aprog] Updated MathTools nCk function.

git-svn-id: https://aprog.svn.sourceforge.net/svnroot/aprog/trunk@187 7cbf5e2b-b55d-4b93-acdd-c0d7b961df51
---
 Aprog/src/net/sourceforge/aprog/tools/MathTools.java      | 14 +++++++++++---
 Aprog/test/net/sourceforge/aprog/tools/MathToolsTest.java |  3 +++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/Aprog/src/net/sourceforge/aprog/tools/MathTools.java b/Aprog/src/net/sourceforge/aprog/tools/MathTools.java
index 94eeeff..38975a6 100644
--- a/Aprog/src/net/sourceforge/aprog/tools/MathTools.java
+++ b/Aprog/src/net/sourceforge/aprog/tools/MathTools.java
@@ -24,6 +24,8 @@
 
 package net.sourceforge.aprog.tools;
 
+import static java.lang.Math.min;
+
 /**
  * @author codistmonk (creation 2011-06-11)
  */
@@ -118,15 +120,21 @@ public final class MathTools {
      * @param n
      * <br>Range: <code>[0L .. Long.MAX_VALUE]</code>
      * @param k
-     * <br>Range: <code>[0L .. k]</code>
+     * <br>Range: <code>[0L .. n]</code>
      * @return <code>n!/(k!(n-k)!)</code>
      * <br>Range: <code>[0L .. Long.MAX_VALUE]</code>
      */
     public static final long nCk(final long n, final long k) {
-        long numerator = n - k + 1L;
+        final long m = min(k, n - k);
+        
+        if (m == 0) {
+            return 1L;
+        }
+        
+        long numerator = n - m + 1L;
         long result = numerator;
         
-        for (long i = 2L; i <= k; ++i) {
+        for (long i = 2L; i <= m; ++i) {
             result = result * (++numerator) / i;
         }
         
diff --git a/Aprog/test/net/sourceforge/aprog/tools/MathToolsTest.java b/Aprog/test/net/sourceforge/aprog/tools/MathToolsTest.java
index 197c500..c6c81e4 100644
--- a/Aprog/test/net/sourceforge/aprog/tools/MathToolsTest.java
+++ b/Aprog/test/net/sourceforge/aprog/tools/MathToolsTest.java
@@ -64,7 +64,10 @@ public final class MathToolsTest {
 
     @Test
     public final void testNCk() {
+        assertEquals(1L, MathTools.nCk(0L, 0L));
+        assertEquals(1L, MathTools.nCk(4L, 0L));
         assertEquals(6L, MathTools.nCk(4L, 2L));
+        assertEquals(1L, MathTools.nCk(4L, 4L));
     }
 
 }
\ No newline at end of file
-- 
2.11.4.GIT