CTCI 3.4

/* Using the recursion to implement the algorithm
*/
import java.util.*;

public class Hanoi {
    public void recursehanoi(int n, Tower a, Tower b, Tower c) {
        if(n == 1) { 
            System.out.println("Move the " + a.peek() + "th plate from " + a.name + " to " + c.name);
            c.add(a.remove()); 
        }
        else {
            //Move the top n-1 plates from a to b using c as buffer
            recursehanoi(n-1, a, c, b);
            //Move the last n from a to c
            System.out.println("Move the " + a.peek() + "th plate from " + a.name + " to " + c.name);
            c.add(a.remove()); 
            //Move the rest n-1 plates from b to c using a as buffer
            recursehanoi(n-1, b, a, c);
        }
    }

    public class Tower {
        public String name;
        public Stack<Integer> plates = new Stack<Integer>();
        public Tower(String name) {
            this.name = name;
        }

        public void add(int plate) {
            plates.push(plate);
        }

        public int peek() {
            return plates.peek();
        }

        public int remove() {
            return plates.pop();
        }
    }

    public static void main(String[] args) {
        Hanoi ha = new Hanoi();
        Hanoi.Tower a = new Hanoi().new Tower("a"); a.add(3); a.add(2); a.add(1);
        Hanoi.Tower b = new Hanoi().new Tower("b"); Hanoi.Tower c = new Hanoi().new Tower("c");
        ha.recursehanoi(3, a, b, c);
    }
}