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authorMattias Andrée <maandree@operamail.com>2014-01-20 00:44:03 +0100
committerMattias Andrée <maandree@operamail.com>2014-01-20 00:44:03 +0100
commit27ef1844cbad9b53283b6d1c0b7a08a4b4271d2a (patch)
treeb6d269b7cbf125d65fc1902620371dc1377c8352 /src/algorithms
parentadd reverse (diff)
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add rotate
Signed-off-by: Mattias Andrée <maandree@operamail.com>
Diffstat (limited to 'src/algorithms')
-rw-r--r--src/algorithms/arrays/Rotate.java66
1 files changed, 66 insertions, 0 deletions
diff --git a/src/algorithms/arrays/Rotate.java b/src/algorithms/arrays/Rotate.java
new file mode 100644
index 0000000..22ba033
--- /dev/null
+++ b/src/algorithms/arrays/Rotate.java
@@ -0,0 +1,66 @@
+/**
+ * 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.*;
+
+
+/**
+ * Class for rotating arrays
+ */
+public class Rotate
+{
+ /*
+ * There are many thing you can change in this class to adapt it, for example,
+ * if you want in-place rotation, which probabily is a bit slower (even though
+ * it is less naïve), you can reverse the array, split it at the index 'steps',
+ * and reverse those partitions and the concatinate back again, of cause, you
+ * would only reverse parts of the array, not split and concatinate it.
+ * You could also reverse the array while rotating it, either reverse the
+ * input or the output.
+ */
+
+
+£<for T in boolean char byte short int long float double T; do
+ P= O="$T" cast=
+£>[ $T = T ] && P="<T> " O=Object cast="(T[])"
+ /**
+ * Rotates an array
+ *
+ * @param items The array to rotate
+ * @param steps The number of steps to higher index to rotate elements
+ * @return The array rotated
+ */
+£>[ $T = T ] &&
+ @SuppressWarnings("unchecked")
+ public static £{P}£{T}[] rotateClone(£{T}[] items, int steps)
+ {
+ £{O}[] rc = new £{O}[items.length];
+
+ int n = items.length;
+ if ((n & -n) == n) /* power of 2 */
+ for (int i = 0, m = n - 1; i < n; i++)
+ rc[(steps + i) & m] = items[i];
+ else
+ for (int i = 0; i < n; i++)
+ rc[(steps + i) % n] = items[i];
+
+ return £{cast}rc;
+ }
+£>done
+}
+