Reverse String II done

Author: rampatra

src/main/java/com/leetcode/strings/RansomNote.java

@@ -36,4 +36,4 @@ public static void main(String[] args) {
         System.out.println(canConstruct("ab", "ab"));
         System.out.println(canConstruct("aab", "ab"));
     }
-}
+}

src/main/java/com/leetcode/strings/ReverseStringII.java

@@ -0,0 +1,51 @@
+package com.leetcode.strings;
+
+/**
+ * Problem: https://leetcode.com/problems/reverse-string-ii/
+ * 
+ * @author rampatra
+ * @since 2019-04-20
+ */
+public class ReverseStringII {
+
+    /**
+     * Time complexity: O(n)
+     * where,
+     * n = no. of characters in string
+     * <p>
+     * Runtime: <a href="https://leetcode.com/submissions/detail/223714484/">0 ms</a>.
+     *
+     * @param str
+     * @param k
+     * @return
+     */
+    public static String reverseStr(String str, int k) {
+        char[] chars = str.toCharArray();
+        int len = str.length();
+        int i = 0;
+        while (i < len) {
+            if (len - i + 1 >= 2 * k) {
+                reverse(chars, i, i + k);
+            } else {
+                reverse(chars, i, Math.min(len, i + k));
+            }
+            i += 2 * k;
+        }
+        return new String(chars);
+    }
+
+    private static void reverse(char[] chars, int start, int end) {
+        char temp;
+        for (int i = start, j = end - 1; i < j; i++, j--) {
+            temp = chars[i];
+            chars[i] = chars[j];
+            chars[j] = temp;
+        }
+    }
+
+    public static void main(String[] args) {
+        System.out.println(reverseStr("abcdefg", 2));
+        System.out.println(reverseStr("abcdef", 2));
+        System.out.println(reverseStr("abcde", 2));
+    }
+}