aula 9 dequeue 2

Estrutura de DadosTAD DequeMaikol M. RodriguesTurmas A e B (UNIFOR)

Gladys Castillo Jordn

Fila de duas Extremidades (Deque) Uma Deque suporta inseres e delees de ambas as extremidades.

The Deque Abstract Data TypeinsertFirst(e): Insero no incio do deque.insertLast(e):Insero no final do dequeremoveFirst():Remove e retorna o primeiro elementoremoveLast(): Remove e retorna o ltimo elemento

Adicionamente pode-se acrescentar os seguintes mtodos:first()last()size()isEmpty()


Fila de duas Extremidades public interface Deque { public int size();public Object first() throws DequeEmptyException; public Object last() throws DequeEmptyException;public boolean isEmpty(); public void insertLast(Object o); public void insertFirst(Object o); public Object removeLast() throwsDequeEmptyException; public Object removeFist() throwsDequeEmptyException; }


Fila de duas Extremidades public class DequeEmptyException extends RuntimeException { public DequeEmptyException(String err) { super(err); }}


Implementando Deque com Lista Duplamente Encadeada (LDE) Deleo do ltimo elemento de uma lista simplesmente encadeada no pode ser feito em tempo constante.Para implementar o Deque utilizaremos uma lista duplamente encadeada com dois ns SENTINELAS.


Classe DLNode class DLNode { private Object element; private DLNode next, prev;

DLNode() { this(null, null, null); }

DLNode(Object e, DLNode p, DLNode n) { element = e; next = n; prev = p; }


Classe DLNode

void setElement(Object newElem){element = newElem;}void setNext(DLNode newNext) { next = newNext; }void setPrev(DLNode newPrev) { prev = newPrev; }Object getElement() { return element; }DLNode getNext() { return next; }DLNode getPrev() { return prev; }

}


Deque usando LDE public class MyDeque implements Deque { DLNode header, trailer; // sentinels int size; // number of elements public MyDeque() { header = new DLNode(); trailer = new DLNode(); header.setNext(trailer); // make header point to trailer trailer.setPrev(header); // make trailer point to header size = 0; }


Deque usando LDE public boolean isEmpty() { return (size==0); } public Object first() throws DequeEmptyException { if (isEmpty()) throw new DequeEmptyException("Deque is empty."); return header.getNext().getElement(); } public Object last() throws DequeEmptyException { if (isEmpty()) throw new DequeEmptyException("Deque is empty."); return trailer.getPrev().getElement(); }


Deque usando LDE public void insertFirst(Object o) { DLNode second = header.getNext(); DLNode first = new DLNode(o, header, second); second.setPrev(first); header.setNext(first); size++; }


Deque usando LDE public Object removeLast() throws DequeEmptyException { if (isEmpty()) throw new DequeEmptyException("Deque is empty."); DLNode last = trailer.getPrev(); Object o = last.getElement(); DLNode secondtolast = last.getPrev(); trailer.setPrev(secondtolast); secondtolast.setNext(trailer); size--; return o; }


Deque usando LDE (removeLast)Aqui uma visualizao do removeLast().


Exerccios de Reviso


Exerccios


Deque usando LDE public void insertLast(Object o) { DLNode ant = trailer.getPrev(); DLNode last = new DLNode(o, ant, trailer); trailer.setPrev(last); ant.setNext(last); size++; }


RemoveFirst public Object removeFirst() throws DequeEmptyException { if (isEmpty()) throw new DequeEmptyException("Deque is empty."); DLNode first = header.getNext(); Object o = first.getElement(); DLNode second = first.getNext(); header.setNext(second); second.setPrev(header); size--; return o; }


Implementao de Pilha e Fila com DequeStacks with Deques:Queues with Deques:


Implementao de Pilha com Deque public class DequeStack implements Stack { private MyDeque D; public DequeStack() { D = new MyDeque(); } public int size() { return D.size(); } public boolean isEmpty() { return D.isEmpty(); } public void push(Object obj) { D.insertLast(obj); }


Implementao de Pilha com Deque public Object top() throws StackEmptyException { try { return D.last(); } catch (DequeEmptyException e) { throw new StackEmptyException("Stack is empty!"); } } public Object pop() throws StackEmptyException { try { return D.removeLast(); } catch (DequeEmptyException e) { throw new StackEmptyException("Stack is empty!"); } }


Implementao de Pilha com Deque public static void main(String args[]) { DequeStack A1 = new DequeStack(); Character b = new Character('A'); Integer c = new Integer(9); A1.push(new Integer(3)); A1.push(b); A1.push(c); System.out.println(A1.pop() + "\n" + A1.pop() + "\n" + A1.pop() + "\n"); if (A1.isEmpty()) System.out.println("A Pilha esta VAZIA... "); if (A1.isEmpty()) System.out.println("A Pilha esta VAZIA... "); } }


Exerccios


Exerccios public static int maior(int[] a, int pos, int maior) { if (pos == a.length) return maior; else if (a[pos] > maior) return maior(a, (pos+1), a[pos]); else return maior(a, (pos+1), maior); }


aula 9 dequeue 2

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