[Leetcode] 541. Reverse String II 解题报告

题目：

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]
思路：

哈哈，练手题目。

代码：

class Solution {
public:
string reverseStr(string s, int k) {
int length = s.length();
for (int i = 0; i < length; i += 2 * k) {
reverseStr(s, i, min(length - 1, i + k - 1));
}
return s;
}
private:
void reverseStr(string &s, int start, int end) {
while (start < end) {
swap(s[start++], s[end--]);
}
}
};