541. 反转字符串2 Reverse String II

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.

Input: s = "abcdefg", k = 2
Output: "bacdfeg"    

Restrictions:

1. The string consists of lower English letters only.
2. Length of the given string and k will in the range [1, 10000]

   public class Solution {
       public string ReverseStr(string s, int k) {
   		char[] cArr = s.ToArray();
   		for (int left = 0; left < cArr.Length; left += 2 * k) {
   			for (int i = left, j = Math.Min(left + k - 1, cArr.Length - 1); i < j; i++, j--) {
   				char tmp = cArr[i];
   				cArr[i] = cArr[j];
   				cArr[j] = tmp;
   			}
   		}
   		return new string(cArr);
       }
   }

   
   

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