Reverse String II

这个题就是处理麻烦，想写的简单难

class Solution(object):
    def reverseStr(self, s, k):
        """
        :type s: str
        :type k: int
        :rtype: str
        """
        tmp = list(s)
        for i in xrange(0, len(s), 2 * k):
            tmp[i : i + k] = reversed(tmp[i:i + k])
        return ''.join(tmp)