Lintcode: Rotate String

Given a string and an offset, rotate string by offset. (rotate from left to right)
 
Example
Given "abcdefg"
 
for offset=0, return "abcdefg"
 
for offset=1, return "gabcdef"
 
for offset=2, return "fgabcde"
 
for offset=3, return "efgabcd"

需要注意的是：if (A.length == 0) return new char[0]; 空数组

 public class Solution {
     /*
      * param A: A string
      * param offset: Rotate string with offset.
      * return: Rotated string.
      */
     public char[] rotateString(char[] A, int offset) {
         // wirte your code here
         if (A==null || A.length == 0) return new char[0];
         String str = new String(A);
         offset %= str.length();
         if (offset == 0) return str.toCharArray();
         String first = str.substring(0, str.length()-offset);
         String second = str.substring(str.length()-offset);
         String res = second + first;
         return res.toCharArray();
     }
 };

法二（推荐）：

 public class Solution {
     /**
      * @param str: an array of char
      * @param offset: an integer
      * @return: nothing
      */
     public void rotateString(char[] str, int offset) {
         // write your code here
         if (str==null || str.length==0) return;
         offset %= str.length;
         if (offset == 0) return;
         reverse(str, 0, str.length-1);
         reverse(str, 0, offset-1);
         reverse(str, offset, str.length-1);
     }
 
     public void reverse(char[] str, int l, int r) {
 
         while (l < r) {
             char temp = str[l];
             str[l] = str[r];
             str[r] = temp;
             l++;
             r--;
         }
     }
 }