Interfaz para pilas Un interfaz y varias implementaciones

,QWHUID]SDUDSLODV
public interface Stack {
public int size();
public boolean isEmpty();
public void push(Object o);
public Object pop()
throws StackEmptyException;
public Object top()
throws StackEmptyException;
}
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
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8QLQWHUID]\
YDULDVLPSOHPHQWDFLRQHV
Stack
ArrayStack
Copyright © 2001 cdk@it.uc3m.es
LinkedStack
Java: Pilas y Colas /
2
1
,PSOHPHQWDFLyQ
EDVDGDHQDUUD\V
S
toptoptoptoptoptop
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2 3
4
5
0
1
3
4
2
5
Copyright © 2001 cdk@it.uc3m.es
N-1
Java: Pilas y Colas /
3
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public class ArrayStack implements Stack {
public static final int CAP=1000;
private int capacity;
private Object S[];
private int top=-1;
public ArrayStack(){this(CAP);}
public ArrayStack(int cap){
capacity=cap;
S=new Object[capacity];}
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
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2
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public int size()
{return (top+1);}
public boolean isEmpty()
{return (top<0);}
public Object top()
throws StackEmptyException {
if (isEmpty())
throw new StackEmptyException("vacio"};
return S[top];}
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
5
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public void push(Object o)
throws StackFullException {
if (size()==capacity)
throw new StackFullException("lleno");
S[++top]=o;}
public Object pop()
throws StackEmptyException {
Object el;
if (isEmpty())
throw new StackEmptyException("vacio"};
el=S[top]; S[top--]=null; return el;}
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
6
}
3
,PSOHPHQWDFLyQEDVDGD
HQOLVWDVHQFDGHQDGDV
Madrid
Miami
Múnich
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
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class Node {
private Object elem;
private Node next;
public Node(Object e, Node n) {
elem=e; next=n;}
void setElem(Object e) {elem=e;}
void setNext(Node n)
{next=n;}
Object getElem() {return elem;}
Node
getNext() {return next;}
}
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
8
4
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public class LinkedStack implements Stack {
private Node top;
private int size;
public LinkedStack() {top=null; size=0;}
public int size() {return size;}
public boolean isEmpty() {
return(top==null);}
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
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Java: Pilas y Colas /
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public void push(Object e) {
Node n=New Node();
n.setElem(e);
n.setNext(top);
top=n;
size++;
}
Copyright © 2001 cdk@it.uc3m.es
5
,QVHUFLyQpush
top
Madrid
Miami
Múnich
Moscú
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
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public Object top()
throws StackEmptyException {
if (isEmpty())
throw new
StackEmptyException("vacia");
return top.getElem();
}
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
12
6
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public Object pop()
throws StackEmptyException {
Object temp;
if (isEmpty())
throw new StackEmptyException("vacia");
temp=top.getElem();
top=top.getNext();
size--;
return temp;
}
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
13
%RUUDGRpop
top
Moscú
Copyright © 2001 cdk@it.uc3m.es
Madrid
Miami
Múnich
Java: Pilas y Colas /
14
7
3LODV\UHFXUVLyQ
❚ public static long fac (int n)
{if (n<=1)
return 1;
else
return n*fac(n-1);
}
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
15
(MHFXFLyQ
❚
❚
❚
❚
❚
❚
❚
❚
fac(4)
4*fac(3)
4*(3*fac(2))
4*(3*(2*fac(1)))
4*(3*(2*1)))
4*(3*2)
4*6
24
Copyright © 2001 cdk@it.uc3m.es
2*
3*
4*
Java: Pilas y Colas /
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8
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Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
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(MHPSOR
❚ /DFRODGHODXWRE~V
❚ /DFRODGHODLPSUHVRUD
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
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9
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❚ (VWUXFWXUDOLQHDO
❚ $FFHVRGHLQVHUFLyQSRUXQH[WUHPR\
GHHOLPLQDFLyQSRUHORWURH[WUHPR
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
19
,QWHUID]SDUDFRODV
public interface Queue {
public int size();
public boolean isEmpty();
public void enqueue(Object o);
public Object dequeue()
throws QueueEmptyException;
public Object front()
throws QueueEmptyException;
}
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
20
10
8QLQWHUID]\
YDULDVLPSOHPHQWDFLRQHV
Queue
ArrayQueue
LinkedQueue
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
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,QVHUFLyQenqueue
top
tail
Madrid
Copyright © 2001 cdk@it.uc3m.es
Miami
Múnich
Moscú
Java: Pilas y Colas /
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11
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public void enqueue(Object e) {
Node n=New Node();
n.setElem(e);
n.setNext(null);
if (size==0)
top=n;
else
tail.setNext(n);
tail=n;
size++;
}
Copyright © 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
23
public Object dequeue()
throws QueueEmptyException {
Object temp;
if (isEmpty())
throw new QueueEmptyException("vacia");
temp=top.getElem();
top=top.getNext();
size--;
if (size==0)
tail=null
return temp;
}
Copyright
© 2001 cdk@it.uc3m.es
Java: Pilas y Colas /
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