public class TowerOfHanoi
{

        int[] ace;
        int[] dos;
        int[] thrice;
        int first;
        int second;
        int third;

    /* Construct the Towers of Hanoi (3 towers) with aNumDisc
     * on the first tower. Each tower can be identified by an
     * integer number (0 for the first tower, 1 for the second
     * tower, and 2 for the third tower). Each disc can be identified
     * by an integer number starting from 0 (for the smallest disc)
     * and (aNumDisc - 1) for the largest disc.
     */
    public TowerOfHanoi(int aNumDiscs)
    {
                ace = new int[aNumDiscs];
                for(int i = 0; i < aNumDiscs; i++){
                    ace[i] = aNumDiscs - 1 - i;
                }
                dos = new int[aNumDiscs];
                dos[0] = aNumDiscs;
                thrice = new int[aNumDiscs];
                thrice[0] = aNumDiscs;
                first = aNumDiscs;
                second = 0;
                third = 0;
    }

    /* Returns an array of integer representing the order of
     * discs on the tower (from bottom up). The bottom disc should
     * be the first element in the array and the top disc should be
     * the last element of the array. The size of the array MUST
     * be the number of discs on the tower. For example, suppose
     * the tower 0 contains the following discs 0,1,4,6,7,8 (from top
     * to bottom). This method should return the array [8,7,6,4,1,0]
     * (from first to last).
     * @param tower the integer identify the tower number.
     * @return an array of integer representing the order of discs.
     */
    public int[] getArrayOfDiscs(int tower)
    {
            int[] tempTower;
        if(tower == 0){
                    tempTower = new int[first];
                    for(int i = 0; i < first; i++){
                        tempTower[i] = ace[i];
                    }
                    return tempTower;
                }
                if(tower == 1){
                    tempTower = new int[second];
                    for(int i = 0; i < second; i++){
                        tempTower[i] = dos[i];
                    }
                return tempTower;
                }
                if(tower == 2){
                    tempTower = new int[third];
                    for(int i = 0; i < third; i++){
                        tempTower[i] = thrice[i];
                    }
                    return tempTower;
                }
                return ace;
    }
    public boolean moveTopDisc(int fromTower, int toTower)
    {
        if((fromTower == 0 && first == 0)||(fromTower == 1 && second == 0)
                        || (fromTower == 2 && third == 0)){
                    return false;
                }
                if(fromTower == 0){
                    if(toTower == 1){
                            if(second != 0&&ace[first-1]>dos[second-1]){
                            return false;
                        }
                        else{
                            dos[second]=ace[first-1];
                            ace[first-1] = 0;
                            first--;
                            second++;
                            return true;
                        }
                    }
                    if(toTower == 2){
                        if(third != 0&&ace[first-1] > thrice[third-1]){
                            return false;
                        }
                        else{
                            thrice[third] = ace[first-1];
                            ace[first-1] = 0;
                            first--;
                            third++;
                            return true;
                        }
                        }
                    }
                if(fromTower == 1){
                    if(toTower == 0){
                        if(first != 0&&dos[second-1]>ace[first-1]){
                            return false;
                        }
                        else{
                            ace[first]=dos[second-1];
                            dos[second-1] = 0;
                            second--;
                            first++;
                            return true;
                        }
                    }
                        if(toTower == 2){
                        if(third!= 0&&dos[second-1] > thrice[third-1]){
                            return false;
                        }
                        else{
                            thrice[third] = dos[second-1];
                            dos[second-1] = 0;
                            second--;
                            third++;
                            return true;
                        }
                        }

                    }

                if(fromTower == 2){
                    if(toTower == 0){
                        if(first !=0 && ace[first-1]>dos[second-1]){
                            return false;
                        }
                        else{
                            ace[first]=thrice[third-1];
                            thrice[third-1] = 0;
                            third--;
                            first++;
                            return true;
                        }
                    }
                    if(toTower == 1){
                        if(third !=0&&thrice[third-1] > dos[second-1]){
                            return false;
                        }
                        else{
                            dos[second] = thrice[third-1];
                            thrice[third-1] = 0;
                            third--;
                            second++;
                            return true;
                        }
                        }
                    }

                    return false;
    }

    /* Gets the total number of discs in this Towers of Hanoi
     * @return the total number of discs in this Towers of Hanoi
     */
    public int getNumberOfDiscs()
    {
        return first+second+third;
    }

    /* Gets the number of discs on a tower.
     * @param tower the tower identifier (0, 1, or 2)
     * @return the number of discs on the tower.
     */
    public int getNumberOfDiscs(int tower)
    {
        if(tower == 0){
                    return first;
                }
                if(tower == 1){
                    return second;
                }
                if(tower == 2){
                    return third;
                }
                return 0;
    }

}