// implement a priority queue using a linked list
// first item on list is the highest priority item

public class PQAsList implements SeqStructure{
    
    private SLL list;
    private int size;

    public PQAsList() { 
        list = new SLL();
    }
        
    // enqueue: put o at end of list:
    public void put(Object o) {
        list.add(o);
        size++;
    }
    
    // dequeue: remove 1st occurrence of largest element in list:
    public Object get() {
        if (isEmpty()) {
            System.out.print("Empty!");
            return null;
        }
	// search list, starting from head:
        ListNode n = list.getHead();
	Object max = n.getItem(); // assume head's item is biggest
	ListNode next = n.getNext();
	// find and update max:
	while (next != null) {	    
	    Object current = next.getItem();
	    int comp = ((Comparable)current).compareTo(max);
	    if (comp > 0) max = current;
	    next = next.getNext();
	}	    
	list.remove(max);
        size--;
        return max;
    }
    
    // empty PQ means empty list:
    public boolean isEmpty() {
        return list.isEmpty();
    }
    
    // return number of elements:
    public int size() {
        return size;
    }
    
    // Stringify:
    public String toString() {
        return "PQ: ["+list+"]";
    }
    
}