From 68bb2db6fb99e3be8640334ddc18297d090ecbf0 Mon Sep 17 00:00:00 2001
From: shellhub <shellhub.me@gmail.com>
Date: Sun, 30 Aug 2020 20:03:07 +0800
Subject: [PATCH 1/2] rotation string

---
 strings/Rotation.java | 64 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 strings/Rotation.java

diff --git a/strings/Rotation.java b/strings/Rotation.java
new file mode 100644
index 00000000..e1f0046f
--- /dev/null
+++ b/strings/Rotation.java
@@ -0,0 +1,64 @@
+package strings;
+
+
+/**
+ * Given a string, moving several characters
+ * in front of the string to the end of the string.
+ * For example, move the two characters'a' and 'b' in
+ * front of the string "abcdef" to the end of the string,
+ * so that the original string becomes the string "cdefab"
+ */
+public class Rotation {
+    public static void main(String[] args) {
+        assert rotation("abcdef", 2).equals("cdefab");
+
+        char[] values = "abcdef".toCharArray();
+        rotation(values, 2);
+        assert new String(values).equals("cdefab");
+    }
+
+    /**
+     * Move {@code n} characters in front of given string to the end of string
+     * time complexity: O(n)
+     * space complexity: O(n)
+     *
+     * @param s given string
+     * @param n the total characters to be moved
+     * @return string after rotation
+     */
+    public static String rotation(String s, int n) {
+        return s.substring(n) + s.substring(0, n);
+    }
+
+    /**
+     * Move {@code n} characters in front of given character array to the end of array
+     * time complexity: O(n)
+     * space complexity: O(1)
+     *
+     * @param values given character array
+     * @param n      the total characters to be moved
+     */
+    public static void rotation(char[] values, int n) {
+        reverse(values, 0, n - 1);
+        reverse(values, n, values.length - 1);
+        reverse(values, 0, values.length - 1);
+    }
+
+    /**
+     * Reverse character array
+     *
+     * @param values character array
+     * @param from   begin index of given array
+     * @param to     end index of given array
+     */
+    public static void reverse(char[] values, int from, int to) {
+        while (from < to) {
+            char temp = values[from];
+            values[from] = values[to];
+            values[to] = temp;
+            from++;
+            to--;
+        }
+    }
+
+}

From c4a4b67d087b6058a1ea4b3486f28b3f1f3058df Mon Sep 17 00:00:00 2001
From: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Date: Tue, 8 Sep 2020 01:31:23 +0000
Subject: [PATCH 2/2] updating DIRECTORY.md

---
 DIRECTORY.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/DIRECTORY.md b/DIRECTORY.md
index 0f2e3528..e9c51452 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -241,4 +241,5 @@
   * [Palindrome](https://github.com/TheAlgorithms/Java/blob/master/strings/Palindrome.java)
   * [Pangram](https://github.com/TheAlgorithms/Java/blob/master/strings/Pangram.java)
   * [ReverseString](https://github.com/TheAlgorithms/Java/blob/master/strings/ReverseString.java)
+  * [Rotation](https://github.com/TheAlgorithms/Java/blob/master/strings/Rotation.java)
   * [Upper](https://github.com/TheAlgorithms/Java/blob/master/strings/Upper.java)