ISD UAS 2 QUEUE.ppt

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CS2014 Data Structure andAlgorithm

Queue Data Structure


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Apa yang dimaksud queue ?

Apa kegunaan queues ?

Properti apa saja yang dimiliki queues ? Bagaimana implementasinya?


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Apa yang dimaksud queue ?

Queue adalah list yang memiliki aturanmain dalam proses inserted dan removeddata. Istilah lain: FIFO (first in first out)

Insertion atau penambahan data hanyadilakukan di salah satu ujung list (rear) dandeletions hanya dilakukan di ujung lainnya(front)

Queue menyerupai sebuah antrian dalamdunia nyata


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Apa kegunaan queue ?

Mengatur layanan terhadap suatu taskdalam suatu sistem agar tercipta fairtreatment

client-server systems

operating systems: antrian task, contohantrian untuk mencetak (printing).

simulation and modeling: contoh air trafficcontrol, urban transport .


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Desain abstrak

Abstract Data Type (ADT):

Kumpulan struktur data bersamaan dengan

Kumpulan operasi terhadap struktur data

tersebut

Data structures:

Biasanya bertipe komposit

Formasi dari structs, arrays, strings, dll. Struktur data berkait dengan menggunakan

pointer


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Queue ADT

State abstractly what the operations do,without saying in detail how they areaccomplished.


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Queue ADT

Sebuah queueQ, dari item-item bertipe T adalah deretanitem bertipe T yang memiliki operasi-operasi sebagaiberikut:

1. Inisialisasi queueQ menjadi emptyqueue.2. Menentukan sebuah queue kosong atau tidak,Q, is

empty.

3. Menentukan sebuah queue penuh atau tidak,Q, isfull.

4. Menyisipkan item baru pada ujung belakang (rear)queue,Q.

5. JikaQ tidak kosong, hapus sebuah item pada ujungdepan queue,Q,(front).


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Queue ADT interface

/* File: Queue.h */

typedef char ItemType ;

typedef struct Queue Queue ;

/* Defined Operations */

extern Queue *QueueNew ( void );

/* Initialize the queue Q to be the empty queue. */

extern int QueueEmpty ( Queue *Q );

/* Returns 1 (True) if (and only if) the queue Q is empty*/

extern int QueueFull ( Queue *Q );

/* Returns 1 (True) if (and only if) the queue Q is full */

extern void QueueInsert ( ItemType R, Queue *Q );/* If Q is not full, insert new item R onto the end of Q */

extern void QueueRemove ( Queue *Q, ItemType *F );

/* If Q is not empty, remove its first item, put it in F. */


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Implementasi Queue

Untuk representasi sekuensial menggunakan array:


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Queues dengan Circular

Track


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Queues dengan Circular

TrackBagaiman implementasi dalam program?

Menggunakan linear array berukuran N.

Menggunakan modular arithmetic: ekspresi X %

N menghasilkan nilai X tetap dalam range 0..N-1.

Set Rear: tambahkan nilai rear lama dengan 1; jikarear=N, set dengan 0.

Rear = (Rear + 1) % N;

Hal yang sama untuk Front: Front = (Front + 1) %N;


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Sequential Queue Representation (I)

Definisikan MAXQUEUESIZE sebagai konstanta.

Sebuah queue merupakan struct yang mengandung: number of items pada queue sebagai Count member

Array item queue sebagai Items member

Array indeks (Front) Array indeks (Rear)

File Queue.c berisi definisi dan operasi QueueNew,QueueEmpty, QueueFull, QueueInsert danQueueRemove (slide sebelumnya)


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/* File: Queue.c */

#include

#include

#include "Queue.h"#define MAXQUEUESIZE 100

struct Queue {

int Count, Front, Rear;

ItemType Items[MAXQUEUESIZE];

} ;


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Initialization:

inisialisasi queueQ menjadi queue kosong.

sebuah queue disebut empty jika Count=0.

indeks Front diset = 0.

indeks Rear diset = 0.


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Sequential Queue Representation

/* Initialize the queue Q to be the emptyqueue. */

Queue * QueueNew ( void )

{

Queue *Q = calloc( 1, sizeof( Queue ) ) ;

Q->Count = 0;

Q->Front = 0;

Q->Rear = 0;

return Q ;

}


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Empty test: menentukan sebuah queue kosongatau tidak,Q, is empty. Sebuah queue didefinisikan empty jika Count =0.

/* Returns 1 (True) if (and only if)* the queue Q is empty.

*/

int QueueEmpty ( Queue *Q )

{return ( Q->Count == 0 );

}


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Full test: menentukan sebuah queue penuh atau tidak,Q, is full. sebuah queue didefinisikan full jika Count =

MAXQUEUESIZE.

/* Returns 1 (True) if (and only if)* the queue Q is full.

*/

int QueueFull ( Queue *Q )

{return ( Q->Count == MAXQUEUESIZE );

}


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Insert a new item onto the rear of the queue,Q.

/* If Q is not full, insert a new item R onto rear of Q by:

* 1. storing R in the item array at position Rear;

* 2. incrementing Rear by one (WRAP AROUND!);

* 3. incrementing Count by one.

*/

void QueueInsert (ItemType R, Queue *Q)

{

if (Q->Count == MAXQUEUESIZE) {

printf("INSERT:Not allowed on full queue.\n");exit(1);

} else {

Q->Items[Q->Rear] = R;

Q->Rear = (Q->Rear + 1) % MAXQUEUESIZE;++ (Q->Count);

}

}


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Jika queueQ is not empty, remove sebuah item dari front sebuahQ.

/* If Q is not empty, remove first item and put it in Fby:

* 1. taking F from the item array at position Front;

* 2. incrementing Front by one (WRAP AROUND!);

* 3. decrementing Count by one.*/

void QueueRemove ( Queue *Q, ItemType *F )

{

if ( Q->Count == 0 ) {

printf("REMOVE:Not allowed on empty q.\n");exit(1);

} else {

*F = Q->Items [Q->Front];Q->Front = (Q->Front + 1) % MAXQUEUESIZE;

-- (Q->Count);

}

}


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Using the Queue interface

#include "QueueInterface.h" /* Assume ItemType is char.*/

/* Access operations and types for stacks.*/

int main ( void )

{

Queue *tq; /* Variable TestQueue of type Queue. */

char C;

tq = QueueNew ( ); /* Make tq empty. */QueueInsert ( a, tq );

QueueInsert ( b, tq );

QueueInsert ( c, tq );

QueueRemove ( tq, &C ); printf ( "Just got: %c.\n", C );


QueueInsert ( d, tq );

...

}

= tulis kode tersebut tanpa mengetahui bagaimanaqueue tersebut diimplementasikan.


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int main ( void )

{


char C;

tq = QueueNew ( ); /* Make tq empty. */

QueueInsert ( a, tq );QueueInsert ( b, tq );





...

}

Queue: Empty


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int main ( void )

{


char C;







...

}

Queue: a


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int main ( void )

{


char C;







...

}

Queue: a, b


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int main ( void )

{


char C;







...

}

Queue: a, b, c


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#include "QueueInterface.h" /* Assume ItemType is char.*//* Access operations and types for stacks.*/

int main ( void )

{


char C;







...

}

Queue: b, c Print:Just got: a.


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#include "QueueInterface.h" /* Assume ItemType is char.*//* Access operations and types for stacks.*/

int main ( void )

{


char C;







...

}

Queue: c Print:Just got: b.


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int main ( void )

{


char C;







...}

Queue: c, d


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Linked Queue Representations

Representasi berikut menggunakan pointer padafrontdan rear.

Setiap node terdiri atas item queue yaitu item memberdan links ke node berikutnya pada list, menggunakan

pointer pada link member.


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Linked Queue Implementation

Conditional checks untuk kondisi tertentupada linked queue implementation:


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Linked Queue Representations

/*File: queueTypes.h*/

typedef arbitrary itemType; /*theitemType can be arbitraty*/

typedef struct tQueueNode{

itemType item;struct tQueueNode *address;

}QueueNode;

typedef struct {

QueueNode *front;QueueNode *rear;

}Queue;


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#include QueueInterface.h

/*Initialize the queue Q to be

the empty queue*/void InitializeQueue(Queue *Q)

{

Q->front=NULL;

Q->rear=NULL;

}


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Empty test: menentukan sebuah queuekosong atau tidak,Q, is empty.

Sebuah queue didefinisikan empty jika front

= NULL.

int Empty(Queue *Q)

{return (Q->front==NULL);

}


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Full test: menentukan sebuah queue penuh atau tidak,Q, is full.

/* we assume an already constructed

queue, Q, is not full, since itcould potentially grow as a linkedstructured */

int Full(Queue *Q)

{

return 0;

}


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Insert item baru ke ujung rear suatu queue,Q.void Insert(itemType R, Queue *Q)

{

QueueNode *temp;

/*attempt to allocate a new node*/

temp=(QueueNode*)malloc(sizeof(QueueNode));

if (temp==NULL){

systemError(system storage is exhausted)

} else{

temp->item=R;

temp->address=NULL;

if (Q->rear==NULL){

Q->front=temp;

Q->rear=temp;}else{

Q->rear->address=temp;

Q->rear=temp;

}

}

}


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TerdapatQ tidak kosong, remove sebuah itam dari front sebuah queueQ.

void remove(Queue *Q,itemType *F)

{

QueueNode *temp;

if (Q->front==NULL){

systemErr(attempt to remove item from emptyqueue);

}else{

*F=Q->front->item;

temp=Q->front;

Q->front=temp->address;free(temp);

if (Q->front==NULL) Q->rear=NULL;

}

}


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Queue Applications

Queues pada operating systems

Menggunakan queues sebagai memorybuffers

Queues pada simulation experiments

Clients - servers

Simulating supermarket checkout lines


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References

Lectures stacks and queues. Dept ofComputer Science, University of Bristol,2004

Thomas A. Standish,Data Structures,

Algorithms & Software Principles in C

Addison-Wesley, 1995 p. 253 ff (Chapter

7)

ISD UAS 2 QUEUE.ppt

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