solve problem Reverse String II

Author: P-ppc

README.md

@@ -12,6 +12,7 @@ All solutions will be accepted!
 |804|[Unique Morse Code Words](https://leetcode-cn.com/problems/unique-morse-code-words/description/)|[java/py/js](./algorithms/UniqueMorseCodeWords)|Easy|
 |500|[Keyboard Row](https://leetcode-cn.com/problems/keyboard-row/description/)|[java/py/js](./algorithms/KeyboardRow)|Easy|
 |344|[Reverse String](https://leetcode-cn.com/problems/reverse-string/)|[java/py/js](./algorithms/ReverseString)|Easy|
+|541|[Reverse String II](https://leetcode-cn.com/problems/reverse-string-ii/description/)|[java/py/js](./algorithms/ReverseStringII)|Easy|
 |292|[Nim Game](https://leetcode-cn.com/problems/nim-game/description/)|[java/py/js](./algorithms/NimGame)|Easy|
 |557|[Reverse Words In A String III](https://leetcode-cn.com/problems/reverse-words-in-a-string-iii/description/)|[java/py/js](./algorithms/ReverseWordsInAStringIII)|Easy|
 |104|[Maximum Depth Of Binary Tree](https://leetcode-cn.com/problems/maximum-depth-of-binary-tree/description/)|[java/py/js](./algorithms/MaximumDepthOfBinaryTree)|Easy|

algorithms/ReverseStringII/README.md

@@ -0,0 +1,2 @@
+# Reverse String II
+This problem is easy to solve

algorithms/ReverseStringII/Solution.java

@@ -0,0 +1,27 @@
+class Solution {
+    public String reverseStr(String s, int k) {
+        char[] res = s.toCharArray();
+        int i = 0,
+            length = s.length();
+        
+        while (i < length) {
+            if (i % (2 * k) == 0) {
+                int start = i,
+                    end = i + k - 1;
+                if (end >= length) {
+                    end = length - 1;
+                }
+                while (start < end) {
+                    char temp = res[start];
+                    res[start++] = res[end];
+                    res[end--] = temp;
+                }
+                i = end + 1;
+            } else {
+                i++;
+            }
+        }
+        
+        return new String(res);
+    }
+}

algorithms/ReverseStringII/solution.js

@@ -0,0 +1,29 @@
+/**
+ * @param {string} s
+ * @param {number} k
+ * @return {string}
+ */
+var reverseStr = function(s, k) {
+    let res = s.split(''),
+        i = 0
+    
+    while (i < s.length) {
+        if (i % (2 * k) === 0) {
+            let start = i,
+                end = i + k - 1
+            if (end >= s.length) {
+                end = s.length - 1
+            }
+            while (start < end) {
+                let temp = res[start]
+                res[start++] = res[end]
+                res[end--] = temp
+            }
+            i = end + 1
+        } else {
+            i++
+        }
+    }
+    
+    return res.join('')
+};

algorithms/ReverseStringII/solution.py

@@ -0,0 +1,25 @@
+class Solution(object):
+    def reverseStr(self, s, k):
+        """
+        :type s: str
+        :type k: int
+        :rtype: str
+        """
+        res = list(s)
+        i = 0
+        while i < len(s):
+            if i % (2 * k) == 0:
+                start = i
+                end = i + k - 1
+                if end >= len(s):
+                    end = len(s) - 1
+                while start < end:
+                    res[start], res[end] = res[end], res[start]
+                    start += 1
+                    end -= 1
+                    
+                i = end + 1
+            else:
+                i += 1
+        
+        return ''.join(res)