[leetcode]: 541. Reverse String II

1.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]

翻译：翻转字符串s,参数k，每2k个字符，翻转前k个。如果最后剩下的字符数大于等于k小于2k，翻转前k个。否则不做操作。

2.分析

STL函数reverse

3.代码

string reverseStr(string s, int k) {    if (k <= 1)        return s;    for (int i = 0; i < s.size(); i += 2 * k)        reverse(s.begin() + i, min(s.begin() + i + k, s.end()));    return s;}