Rotate String

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

Example

Given "abcdefg".

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

分析：
利用 （A^TB^T）^T = BA

public class Solution {
    /**
     * @param str: an array of char
     * @param offset: an integer
     * @return: nothing
     */
    public void rotateString(char[] str, int offset) {
        if (str == null || str.length <= 1) return;
        offset = offset % str.length;
        if (offset == 0) return;
        
        int p = str.length - 1 - offset;
        
        swapFromIToJ(str, 0, p);
        swapFromIToJ(str, p + 1, str.length - 1);
        swapFromIToJ(str, 0, str.length - 1);
    }
    
    public void swapFromIToJ(char[] str, int i, int j) {
        while (i < j) {
            char temp = str[i];
            str[i] = str[j];
            str[j] = temp;
            i++;
            j--;
        }
    }
}