# LeetCode - 0541. Reverse String II
### 題目網址：https://leetcode.com/problems/reverse-string-ii/
###### tags: `LeetCode` `Easy` `字串`

/*
    -LeetCode format-
    Problem: 541. Reverse String II
    Difficulty: Easy
    
    by Inversionpeter
*/



class Solution {
    
    void Reverse(string &input, int start, int end) {
        if (end > input.size())
            end = input.size();
        int half = (end + start) >> 1;
        for (int i = start; i < half; ++i)
            swap(input[i], input[end - (i - start) - 1]);
    }
    
public:
    string reverseStr(string s, int k) {
        if (!s.size())
            return "";
        for (int i = 0; i < s.size(); i += (k << 1))
            Reverse(s, i, i + k);
        return s;
    }
};