7. You have to use c++ to solve this problem. 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. Restrictions: 1. The string consists of lower English letters only. 2. Length of the given string and k will in the range [1, 10000] Input: s-"abcdefg", k = 2 Output: "bacdfeg Please write your program with this class: class Solution public: string reverseStr(string s, int k) [