原地旋转字符串

public class Rotation {

	
	public static void rotate(char[] s, int last, int left) throws Exception{
		if(s == null){
			throw new Exception("");
		}
		if(s.length == 0){
			throw new Exception("");
		}
		int right = s.length - 1;
		if(left == right){
			return ;
		}
		if(last<left || last>right){
			return;
		}
		int middle = (left + right)/2;
		if(last < middle){
			for(int i=0; i<=(last-left); i++){
				swap(s, i, left, last);
			}
			int newLast = 2*last -left +1;
			left = last + 1;
			rotate(s, newLast, left);
		}else{
			for(int j=0; j<right-last; j++){
				swap(s, j, left, last);
			}
			left = left + right -last;
			rotate(s, last, left);
		}
	}
	
	private static void swap(char[] s, int k, int left, int last){
		char temp = s[left+k];
		s[left+k] = s[last+1+k];
		s[last+1+k] = temp;
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		String s = "abcdefghijklmn";
		char[] ss = s.toCharArray();
		try {
			Rotation.rotate(ss, 6, 0);
			System.out.println(new String(ss));
		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}