//*************************************************
//
// An example of linked lists, initially for lists of 
// integers. We define the class and appropriate methods
//
//**************************************************

public class IntList {

    private IntNode head;

    public IntList(){
	head = null;
    }
    
    public boolean isEmpty(){return head == null;}

    public String toString(){
	if (isEmpty())
	    return "()";
	else
	    return "(" + head + ")";
    }

    public void add(int data){
	head = new IntNode(data,head);
    }

    public void delete(int e){head = delete(head,e);}

    private IntNode delete(IntNode x, int e) {
	if (x == null)
	    return null;
	else if (x.getData() == e)
	    return delete(x.getNext(),e);
	else {
	    x.setNext(delete(x.getNext(),e));
	    return x;
	}
    }

    public int size(){
	int size =0;
	IntNode nodeHopper = head;
	while (nodeHopper != null){
		nodeHopper = nodeHopper.getNext();
		size++;
	}
	return size;
    }
    //
    // return the number of elements in the list
    // zero if empty
    //

    public int sum(){
	int sum = 0;
	IntNode nodeHopper = head;
	while (nodeHopper != null){
		sum = sum + nodeHopper.getData();
		nodeHopper = nodeHopper.getNext();
	    }
	    return sum;
    }
    //
    // return the sum of the data in the list
    // zero if empty
    //

    public int max() throws IntListException {
	if (isEmpty())
	    throw new IntListException("max of empty list!");
	else {
	    IntNode nodeHopper = head;
	    int max = -9999,
		x = 0;
	    while (nodeHopper != null){
		x = nodeHopper.getData();
		if (x>max)
		    max = x;
		nodeHopper = nodeHopper.getNext();
	    }
	    return max;
	}
    }
    //
    // return the largest data in the list.
    // throw a IntListException if empty
    //

    public boolean isPresent(int e) {return isPresent(head,e);}

    private boolean isPresent(IntNode x, int e){
	return (x != null) &&
	       ((x.getData() == e) || isPresent(x.getNext(),e));
    }

    public void show(){
	System.out.println(this +
			   " isEmpty()=" + isEmpty() +
			   " size()=" + size() +
			   " sum()=" + sum() +
			   " max()=" + max());
    }
		
	    

    public static void main(String[] args) throws Exception {
	
	IntList L1 = new IntList();
	System.out.println(L1.isEmpty() + "  " + L1);
	L1.add(2);
	System.out.println(L1.isEmpty() + "  " + L1);
	L1.add(1);
	System.out.println(L1.isEmpty() + "  " + L1);
	
	IntList L2 = new IntList();
	for (int i=10;i>0;i--)
	    L2.add(i);
	System.out.println(L2.isEmpty() + "  " + L2);

	for (int i=10;i>0;i--)
	    L2.add(i);
	L2.delete(50);
	System.out.println(L2.isEmpty() + "  " + L2);
	
	L1.delete(1);
	System.out.println(L1.isEmpty() + "  " + L1);
	L1.delete(2);
	System.out.println(L1.isEmpty() + "  " + L1);

	L2.show();
	L1.show();

	System.out.println(L2.max());

    }
}