add knuth shuffle

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/src/algorithms/shuffling/KnuthShuffle.java b/src/algorithms/shuffling/KnuthShuffle.java
new file mode 100644
index 0000000..7414e49
--- /dev/null
+++ b/src/algorithms/shuffling/KnuthShuffle.java
@@ -0,0 +1,53 @@
+/**
+ * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package algorithms.arrays;
+
+import java.util.Random;
+
+
+/**
+ * Bias free array shuffling class using Knuth Shuffle.<br>
+ * Sattolo Cycle is an improvement of this method.
+ */
+public class KnuthShuffle
+{
+£>for T in boolean char byte short int long float double Object; do
+    /**
+     * Shuffles an array
+     *
+     * @param  array   The array to shuffle
+     * @param  random  The random generator to use
+     */
+    public static void shuffle(£{T}[] array, Random random)
+    {
+        int i = 0, j;
+        int n = array.length - 1;
+        for (;;)
+	{
+	    if (i == n)
+		break;
+            
+	    £{T} temp = array[i];
+	    array[i] = array[j = random.nextInt(n - i) + i + 1];
+	    array[j] = temp;
+            
+	    i++;
+	}
+    }
+£>done
+}
+