Program Studi Diploma III Teknik Informatika
Fakultas Ilmu Terapan
Telkom University
Dosen: Cahyana, S.T., M.Kom.
•
Apa yang dimaksud queue ?
•
Apa kegunaan queues ?
•
Properti apa saja yang dimiliki queues ?
Apa yang dimaksud queue ?
•
Queue adalah list yang memiliki “aturan main”
dalam proses inserted dan removed data.
•
Konsep queue adalah FIFO (first in first out)
•
Insertion/Enqueue atau penambahan data
hanya dilakukan di salah satu ujung list (rear)
dan deletions/dequeue hanya dilakukan di ujung
lainnya (front)
•
Queue menyerupai sebuah antrian dalam dunia
Apa kegunaan queue ?
•
Mengatur layanan terhadap suatu task dalam
suatu sistem agar tercipta “fair treatment”
▫
client-server systems
▫
operating systems: antrian task, contoh antrian
untuk mencetak (printing).
▫
simulation and modeling: contoh air traffic
control, urban transport .
Queue ADT
Operasi yang mungkin ada pada Queue:
1.
Inisialisasi queue Q menjadi empty queue.
2.
Menentukan sebuah queue kosong atau tidak, Q, is
empty.
3.
Menentukan sebuah queue penuh atau tidak, Q, is full.
4.
Jika Q tidak penuh, sisipkan item baru pada ujung
belakang (rear) queue, Q.
5.
Jika Q tidak kosong, hapus sebuah item pada ujung
depan (front) queue, Q.
Queue ADT interface
/* File: Queue.h */
#define MAXQUEUESIZE 100
struct Queue {
int Count, Front, Rear;
char Items[MAXQUEUESIZE];
};
/* Defined Operations */
Queue *QueueNew ();
/* Initialize the queue Q to be the empty queue. */
int QueueEmpty ( Queue *Q );
/* Returns 1 (True) if (and only if) the queue Q is empty*/
int QueueFull ( Queue *Q );
/* Returns 1 (True) if (and only if) the queue Q is full */
void QueueInsert (char R, Queue *Q );
/* If Q is not full, insert new item R onto the end of Q */
void QueueRemove ( Queue *Q, char *F );
Implementasi Queue
Queues dengan Circular Track
Bagaimana 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; jika
rear=N, set dengan 0.
▫
Rear = (Rear + 1) % N;
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 dan
QueueRemove (slide sebelumnya)
Sequential Queue Representation (I)
Initialization:
•
inisialisasi queue Q menjadi queue kosong.
•
sebuah queue disebut empty jika Count =0.
– Count diset = 0.
– indeks Front diset = 0.
– indeks Rear diset = 0.
Sequential Queue Representation
/* Initialize the queue Q to be the empty queue. */
Queue * QueueNew ()
{
Queue *Q = new Queue;
Q->Count = 0;
Q->Front = 0;
Q->Rear = 0;
return Q ;
}
Sequential Queue Representation
•
Empty test: menentukan sebuah queue kosong
atau 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 );
}
Sequential Queue Representation
•
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 );
}
Sequential Queue Representation
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 (char R, Queue *Q) {
if (Q->Count == MAXQUEUESIZE) {
cout<<"INSERT:Not allowed on full queue.“<<endl; } else {
Q->Items[Q->Rear] = R;
Q->Rear = (Q->Rear + 1) % MAXQUEUESIZE; Q->Count++;
} }
Sequential Queue Representation
Jika queue Q is not empty, remove sebuah item dari front sebuah Q
.
/* If Q is not empty, remove first item and put it in F by:
* 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, char *F )
{
if ( Q->Count == 0 ) {
cout<<“REMOVE:Not allowed on empty q.“<<endl;
} else {
*F = Q->Items [Q->Front];
Q->Front = (Q->Front + 1) % MAXQUEUESIZE;
Q->Count--;
}
}
Using the Queue interface
#include "QueueInterface.h" /* Assume ItemType is char.*/ /* Access operations and types for stacks.*/
int main () {
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 ); QueueRemove ( tq, &C ); printf ( "Just got: %c.\n", C ); QueueInsert ( ’d’, tq );
... }
Orang lain dapat menulis kode di atas tanpa
mengetahui bagaimana queue tersebut
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 ); QueueRemove ( tq, &C ); printf ( "Just got: %c.\n", C ); QueueInsert ( ’d’, tq );
... }
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 ); QueueRemove ( tq, &C ); printf ( "Just got: %c.\n", C ); QueueInsert ( ’d’, tq );
... }
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 ); QueueRemove ( tq, &C ); printf ( "Just got: %c.\n", C ); QueueInsert ( ’d’, tq );
... }
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 ); QueueRemove ( tq, &C ); printf ( "Just got: %c.\n", C ); QueueInsert ( ’d’, tq );
... }
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 ); QueueRemove ( tq, &C ); printf ( "Just got: %c.\n", C ); QueueInsert ( ’d’, tq );
... }
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 ); QueueRemove ( tq, &C ); printf ( "Just got: %c.\n", C ); QueueInsert ( ’d’, tq );
... }
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 );
QueueRemove ( tq, &C ); printf ( "Just got: %c.\n", C );
QueueInsert ( ’d’, tq );
...
}
Linked Queue Representations
•
Representasi berikut menggunakan pointer pada
front dan rear.
•
Setiap node terdiri atas item queue yaitu item
member dan links ke node berikutnya pada list,
menggunakan pointer pada link member.
Linked Queue Implementation
Conditional checks untuk kondisi tertentu pada
linked queue implementation:
Linked Queue Representations
/*File: queueTypes.h*/
typedef struct tQueueNode{
char item;
tQueueNode *address;
} QueueNode;
typedef struct tQueue {
QueueNode *front;
QueueNode *rear;
} Queue;
Linked Queue Implementation
#include “QueueInterface.h”
/*Initialize the queue Q to be the
empty queue*/
void InitializeQueue(Queue *Q)
{
Q->front=NULL;
Q->rear=NULL;
}
Linked Queue Implementation
•
Empty test: menentukan sebuah queue kosong
atau tidak, Q, is empty.
▫
Sebuah queue didefinisikan empty jika front =
NULL.
boolean Empty(Queue *Q)
{
return (Q->front==NULL);
}
Linked Queue Implementation
•
Full test: menentukan sebuah queue penuh atau tidak,
Q, is full.
boolean Full
(
QueueNode *nB
)
{
return (nB==NULL);
}
Linked Queue Implementation
Insert item baru ke ujung rear suatu queue, Q.
void Insert(char R, Queue *Q) {
QueueNode *temp = new QueueNode; if (Full(temp)) {
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; } } }
