import java.util.*;

/**
   A program to solve the towers of hanoi.
 */
public class towers {
    
    /**
     * A method to move n disks from one peg to another.
     * @param disks - the number of disks to move
     * @param from - the index of the peg from which the pegs should be transferred
     * @param to - the index of the peg to which the pegs should be transferred
     * @param using - the intermediate peg
     * @param lists - the array of lists containing info about which disks are on which pegs
     **/
    public static void moveMany(int disks, int from, int to, int using, ArrayList<Integer>[] lists){

	//base case
	//there are no disks to move, so return
	if (disks == 0) {
	    return;
	}
	
	//move n-1 disks to the intermediate peg
	moveMany(disks-1, from, using, to, lists);
	
	//move nth disk to target peg
	moveOne(lists[from-1], lists[to-1]);
		
	//print current state
	printLists(lists);
	
	//move n-1 disks to final peg
	moveMany(disks-1, using, to, from, lists);
    }
    
    /**
     * A method to move one disk.
     * @param fromlist - the list of disks from which the top will be moved
     * @param tolist - the list of disks to which the top of from list will be moved
     **/
    public static void moveOne(ArrayList<Integer> fromlist, ArrayList<Integer> tolist) {
	//remove top peg from fromlist
	int elt = fromlist.remove(0);
	//add top peg to top of tolist
	tolist.add(0, elt);

    }
    
    /**
     * A method to print the current state of the pegs.
     * @param lists - the array containing a list representing the state of each peg
     **/
    public static void printLists(ArrayList<Integer>[] lists) {
	//print contents of first peg 
	System.out.print("[");
	for(int i = 0; i < lists[0].size(); i++) {
	    System.out.print(lists[0].get(i));
	}
	System.out.print("]");
	
	//print contents of second peg
	System.out.print("[");
	for(int i = 0; i < lists[1].size(); i++) {
	    System.out.print(lists[1].get(i));
	}
	System.out.print("]");
	
	//print contents of third peg
	System.out.print("[");
	for(int i = 0; i < lists[2].size(); i++) {
	    System.out.print(lists[2].get(i));
	}
	System.out.println("]");
    }

    /**
     * Main method to run the program.
     * usage: java towers <num_disks>
     **/
    public static void main(String[] args){
	//if user did not enter number of disks as command line argument, print usage and exit
	if (args.length < 1) {
	    System.out.println("usage: java towers <num_disks>");
	    System.exit(1);
	}
	
	//parse number entered by use to int
	int NUM_DISKS = 0;
	try {
	    NUM_DISKS = Integer.parseInt(args[0]);
	} catch(NumberFormatException nfe) {
	    //if user entered a string, print usage and exit
	    System.out.println("usage: java towers <num_disks>");
	    System.exit(1);
	}
	
	//create array of lists representing the state of each peg
	//causes compilation warning, unchecked conversion
	//ignore for now
	ArrayList<Integer>[] lists = new ArrayList[3];
	lists[0] = new ArrayList<Integer>();
	lists[1] = new ArrayList<Integer>();
	lists[2] = new ArrayList<Integer>();

	//add n disks to first peg
	for(int i = 0; i < NUM_DISKS; i++) {		
	    lists[0].add(i+1);
	}
	
	//move n disks from peg 1 to 3 using 2 as intermediate
	moveMany(lists[0].size(), 1, 3, 2, lists);
    }
    
}