汉诺塔问题：打印n层汉诺塔从最左边移动到最右边的全部过程。

    1.     public static void hanoi(int n) {
    2.         if (n > 0) {
    3.             func(n, "left", "right", "mid");
    4.         }
    5.     }
    7.     public static void func(int N, String from, String to, String other) {
    8.         if (N == 1) { // base case 最上面的圆盘想怎么动就怎么动 
    9.             System.out.println("Move 1 from " + from + " to " + to);
    10.         } else {
    11.             func(N - 1, from, other, to);
    12.             System.out.println("Move " + N + " from " + from + " to " + to);
    13.             func(N - 1, other, to, from);
    14.         }
    15.     }