add human shuffle

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

1 files changed, 62 insertions, 0 deletions

diff --git a/src/algorithms/shuffling/HumanShuffle.java b/src/algorithms/shuffling/HumanShuffle.java
new file mode 100644
index 0000000..cfdc6b9
--- /dev/null
+++ b/src/algorithms/shuffling/HumanShuffle.java
@@ -0,0 +1,62 @@
+/**
+ * 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 aiming to imitate naïve shuffling as preformed by humans
+ */
+public class HumanShuffle
+{
+£>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 n;
+	if ((n = array.length) < 2)
+	    return;
+        
+	int min = (int)(random.nextGaussian() * n) >> 1;
+	if (min < 0)
+	    min = n - min;
+	else
+	    min += n;
+        
+	int k = 0;
+	while ((k++ < min) || (random.nextInt(2) == 0))
+	{
+	    int i = random.nextInt(n);
+	    int j = random.nextInt(n);
+
+	    if (i == j)
+		j = (j + 1) % n;
+
+	    £{T} temp = array[i];
+	    array[i] = array[j];
+	    array[j] = temp;
+	}
+    }
+£>done
+}
+