Rotate String

Given a string and an offset, rotate string by offset. (rotate from left to right)

Have you met this question in a real interview? 

Yes

Example

Given "abcdefg".

offset=0 => "abcdefg"
offset=1 => "gabcdef"
offset=2 => "fgabcde"
offset=3 => "efgabcd"

Challenge

Rotate in-place with O(1) extra memory.

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 || offset == 0) return A;

        offset = offset % A.length;

        reverse(A, A.length - offset, A.length-1);

        reverse(A, 0, A.length - offset - 1);

        reverse(A, 0, A.length-1);

        return A;

    }

    private void reverse(char[] A, int i, int j){

        while(i < j){

            char temp = A[i];

            A[i] = A[j];

            A[j] = temp;

            i++; j--;

        }

    }

};