[541] Reverse String II

https://leetcode.com/problems/reverse-string-ii/description/

• algorithms
• Easy (44.48%)
• Source Code: 541.reverse-string-ii.py
• Total Accepted: 57.4K
• Total Submissions: 126.7K
• Testcase Example: '"abcdefg"\n2'

Given a string and an integer k, you need to reverse the first k characters for every 2k characters counting from the start of the string. If there are less than k characters left, reverse all of them. If there are less than 2k but greater than or equal to k characters, then reverse the first k characters and left the other as original.

Example:

Input: s = "abcdefg", k = 2 Output: "bacdfeg"

Restrictions:

The string consists of lower English letters only. Length of the given string and k will in the range [1, 10000]

class Solution(object):
    def reverseStr(self, s, k):
        """
        :type s: str
        :type k: int
        :rtype: str
        """
        lens = len(s)
        result = ''
        for i in range(0, lens+1, 2*k):
            result += s[i:i+k][::-1]
            result += s[i+k:i+2*k]

        return result
#
#
# s = Solution()
# astr = 'abcdefg'
# print s.reverseStr(astr, 2)
#
#