nota queue dari subjek data structure dah diringkaskan | PSMZA .

1. QUEUE

2. Course Objectives
At the end of the lesson students are expected to be able
to:
• Understand queue concepts and applications.
• Understand queue structure and operations that can be
done on queue.
• Understand and know how to implement queue using
array and linked list : linear array, circular array, linear
link list and circular list.

3. 1.0 Introduction to Queue

4. Introduction to Queue
• New items enter at the back, or rear, of the
queue
• Items leave from the front of the queue
• First-in, first-out (FIFO) property
– The first item inserted into a queue is the
first item to leave
– Middle elements are logically inaccessible

5. Introduction to Queue
• Important in simulation & analyzing the
behavior of complex systems

6. Queue Applications
• Real-World Applications
– Cashier lines in any store
– Check out at a bookstore
– Bank / ATM
– Call an airline

7. Queue Applications
• Computer Science Applications
– Print lines of a document
– Printer sharing between computers
– Recognizing palindromes
– Shared resource usage (CPU, memory
access, …)

8. Queue Applications
• Simulation
– A study to see how to reduce the wait
involved in an application

9. Queue implementation
Remove/ Add/
A B C Enqueue
Dequeue
Front/Head Back/Rear
Basic Structure of a Queue:
•Data structure that hold the queue
•head
•rear

10. Queue implementation
Add/
A B C D Enqueue
Head Rear
Insert D into Queue (enQueue) : D is inserted at rear
Remove/
Dequeue A B C D
Head Rear
Delete from Queue (deQueue) : A is removed

11. Queue operations
• Queue operations
– Create an empty queue
– Destroy a queue
– Determine whether a queue is full
– Add a new item to the queue (enQueue)
– Determine whether a queue is empty
– Remove the item that was added earliest(deQueue)
– Retrieve at Front(getFront)
– Retrieve at Back the item that was added
earliest(getRear)

12. Queue Implementation
Implementation:
– Array-based (Linear or Circular)
– Pointer-based : Link list (Linear or
Circular)

13. 2.0 Queue Implementation Using
Array(Linear)

14. Queue Implementation Using
Array(Linear)
• Number of elements in Queue are fixed
during declaration.
• Need isFull() operation to determine
whether a queue is full or not.

15. Queue Implementation Using
Array(Linear)
• Queue structure need at least 3 elements:
1) Element to store items in Queue
2) Element to store index at head
3) Element to store index at rear

16. Create Queue Operation
• Declare
– front & back are indexes in the array
– Initial condition: front =0 & back = -1
– Size of an array in queue
Queue
0 0 1 2 3 Max size -1
front back

17. Create Queue operation
Example Code 1
#include <iostream>
using namespace std;
#define max 5
int front = 0, back = -1;
Create Queue
char item[max], newitem;
item
0 0 1 2 3 4 -1
front back
Front refer to index 0
Continue…

18. enQueue operation
void enQueue(){
cout<<"nt#################n";
cout<<"nt1. enQueuen";
//check queue is full
if(back == max - 1){
cout<<"ntQueue Is Full, Cannot Add Item In Queuen";
}else{
cout<<"nttEnter Item:";
cin>>newitem;
back++;
item[back]=newitem;
cout<<endl; enQueue
}
} item back++
0 0 1 2 3 4 0
front A back
back = -1+1
back = 0
Front refer to index 0 From back/rear
item[back] = newitem
Continue…

19. enQueue operation
item back++
0 0 1 2 3 4 1
front A B back
back = 0 +1
back = 1
Front refer to index 0 From back/rear
item[back] = newitem
item back++
0 0 1 2 3 4 2
front A B C back
back = 1 +1
Front refer to index 0 back = 2
From back/rear
item[back] = newitem
Continue…

20. enQueue operation
item back++
0 0 1 2 3 4 3
front A B C D back
back = 2 +1
back = 3
Front refer to index 0
From back/rear
item[back] = newitem
item back++
0 0 1 2 3 4 4
front A B C D E back
back = 3 +1
back = 4
Front refer to index 0
From back/rear
item[back] = newitem
Continue…

21. deQueue operation
void deQueue(){
cout<<"nt#################n";
cout<<"nt2.deQueuen";
if(back < front){
cout<<"ntThere is no data to remove from queuen";
}else{
char itemdeleted;
itemdeleted=item[front]; deQueue
item[front] = NULL;
cout<<"ntItem Remove From Queue:"<<itemdeleted<<endl;
front++;
}
cout<<endl; item
} 0 0 1 2 3 4 4
front A B C D E back
back = 3 + 1
itemdeleted = item[front] Front refer to index 0 back = 4
front = 0
From front/head
item[front] = NULL Continue…

22. deQueue operation
front++ item
1 0 1 2 3 4 4
front NULL B C D E back
front = 0 + back = 3 + 1
1 back = 4
front = 1
Front refer to index 1
item
1 0 1 2 3 4 4
front NULL B C D E back
back = 3 + 1
Front refer to index 1 back = 4
itemdeleted = item[front]
From front/head
front = 1
item[front] = NULL
front++ item
2 0 1 2 3 4 4
front NULL NULL C D E back
front = 1 + back = 3 + 1
1 back = 4
front = 2
Front refer to index 2 Continue…

23. deQueue operation
item
2 0 1 2 3 4 4
front NULL NULL C D E back
back = 3 + 1
Front refer to index 2 back = 4
From front/head
itemdeleted = item[front] item[front] = NULL
front = 2
front++ item
3 0 1 2 3 4 4
front NULL NULL NULL D E back
front = 2 + back = 3 + 1
1 back = 4
front = 3
Front refer to index 3
Continue…

24. deQueue operation
item
3 0 1 2 3 4 4
front NULL NULL NULL D E back
back = 3 + 1
Front refer to index 3 back = 4
itemdeleted = item[front] From front/head
front = 3 item[front] = NULL
front++ item
4 0 1 2 3 4 4
front NULL NULL NULL NULL E back
front = 3 + back = 3 + 1
1 back = 4
front = 4
Front refer to index 4
Continue…

25. deQueue operation
item
4 0 1 2 3 4 4
front NULL NULL NULL NULL E back
back = 3 + 1
Front refer to index 4 back = 4
itemdeleted = item[front] From front/head
front = 4 item[front] = NULL
front++ item
5 0 1 2 3 4 4
front NULL NULL NULL NULL NULL back
front = 4 + back = 3 + 1
1 back = 4
front = 5
Continue…

26. Retrieve at front(getFront) operation
void getFront(){
cout<<"nt#################n";
cout<<"nt3.getFrontn";
if(back < front){
cout<<"ntThere is no data to at frontn";
}else{
cout<<"ntItem At Front:"<<item[front]<<endl;
}
}
Continue…

27. Retrieve at back(getRear) operation
void getRear(){
cout<<"nt#################n";
cout<<"nt4.getRearn";
if(back < front){
cout<<"ntThere is no data to at rearn";
}else{
cout<<"ntItem At Rear:"<<item[back]<<endl;
}
}
Continue…

28. destroyQueue operation
void destroyQueue(){
delete [] item;
}
Continue…

29. displayQueue operation
void displayQueue(){
cout<<"ntDisplay Item In Queuen";
if(back < front){
cout<<"ntThere is no data in queue to be displayedn";
}else{
cout<<"t";
for(int i=0; i < max; i++ ){
cout<<"t"<<item[i];
}
cout<<endl;
}
}
Continue…

30. Queue Implementation Using Array(Linear)
int main()
{
int selection;
menu:
cout<<"nPlease Choose Your Selectionn";
cout<<"n1tenQueuen";
cout<<"n2tdeQueuen";
cout<<"n3tGetFrontn";
cout<<"n4tGetRearn";
cout<<"n5tDestroyQueuen";
cout<<"n6tDisplayn";
cout<<"ntSelection is:";
cin>>selection;
Continue…

31. Queue Implementation Using Array(Linear)
switch(selection){
case 1: enQueue();
displayQueue();
goto menu;
break;
case 2: deQueue();
displayQueue();
goto menu;
break;
case 3: getFront();
displayQueue();
goto menu;
break;
Continue…

32. Queue Implementation Using Array(Linear)
case 4: getRear();
displayQueue();
goto menu;
break;
case 5: destroyQueue();
displayQueue();
goto menu;
break;
case 6: displayQueue();
goto menu;
break;
default:cout<<"ntWrong Selectionn";
}
return 0;
}

33. Queue Implementation Using Array(Linear)
• Problem: Rightward-Drifting:
• After a sequence of additions & removals,
items will drift towards the end of the array
• enQueue operation cannot be performed
on the queue below, since back = max – 1.
front++ item
5 0 1 2 3 4 4
front NULL NULL NULL NULL NULL back
front = 4 + back = 3 + 1
1 back = 4
front = 5

34. Queue Implementation Using Array(Linear)
• Rightward drifting solutions
– Shift array elements after each deletion
• Shifting dominates the cost of the
implementation

35. Queue Implementation Using Array(Linear)
– Use a circular array: When Front or Back
reach the end of the array, wrap them around
to the beginning of the array
• Problem:
– Front & Back can't be used to
distinguish between queue-full & queue-
empty conditions

36. Queue Implementation Using Array(Linear)
• Solution:
– Use a counter
– Count == 0 means empty queue
– Count == MAX_QUEUE means full
queue

37. 3.0 Queue Implementation Using
Array(Circular)

38. Queue Implementation Using
Array(Circular)
• Number of elements in Queue are fixed
during declaration.
• Need isFull() operation to determine
whether a queue is full or not.

39. Queue Implementation Using
Array(Circular)
• Queue structure need at least 3 elements:
1) Element to store items in Queue
2) Element to store index at head
3) Element to store index at rear
4) Element to store index in counter

40. Create Queue Operation
• Declare
– front & back are indexes in the array
– count to store index
– Initial condition: front =0 , back = -1, count = 0
– Size of an array in queue

41. Queue Implementation Using Array(Circular)
– The Wrap-around effect is obtained by using
modulo arithmetic (%-operator)
front = 0
7 0
6 1
5 2
4 3
back = -1 count = 0

42. Queue Implementation Using Array(Circular)
– enQueue
• Increment back, using modulo arithmetic
• Insert item
• Increment count
– deQueue
• Increment front using modulo arithmetic
• Decrement count
– Disadvantage
• Overhead of maintaining a counter or
flag

43. Queue Implementation Using Array(Circular)
Example Code 2:
queue
#include <iostream> front = 0
using namespace std; 7 0
6 1
#define max 8
char queue[max], newitem;
5 2
int front = 0, back = -1, count = 0;
4 3
back = -1 count = 0
Continue…

44. Queue Implementation Using Array(Circular)
void enQueue(){
cout<<"nt#### enQueue Circular ####n";
if(count == max){
cout<<"ntQueue Circular Is Full!!!n";
}else{
cout<<"ntfront:"<<front<<"t"<<"back:"<<back<<"tcount:"<<count<<“tmax:”<<max<<"n";
cout<<"ntEnter Item:"; front = 0
7 0 back = 0
cin>>newitem;
A
back = (back + 1)% max; 6 1
back = (-1 + 1) % 8
back = 0 % 8
queue[back] = newitem;
back = 0 5 2
count++; 0 queue[0] = A
8√ 0 4 3
} } count = 0 + 1
0 count = 1
count = 1
0 Continue…

45. enQueue Implementation Using Array(Circular)
From previous slide: front = 0, back = 0, count = 1 queue
front = 0
7 0
A back = 1
6 1
back = (0 + 1) % 8 B
back = 1 % 8
back = 1 5 2
0 queue[1] = B
8√ 1 4 3
count = 1 + 1
0 count = 2
1 count = 2
Continue…

46. enQueue Implementation Using Array(Circular)
From previous slide: front = 0, back = 1, count = 2
queue front = 0
7 0
A
6 1
back = (1 + 1) % 8 B
back = 2 % 8
C
back = 2 5 2 back = 2
0 queue[2] = C
8√ 2 4 3
count = 2 + 1
0 count = 3
2 count = 3
Continue…

47. enQueue Implementation Using Array(Circular)
From previous slide: front = 0, back = 2, count = 3
queue
front = 0
7 0
A
6 1
back = (2 + 1) % 8 B
back = 3 % 8
back = 3 C
5 2
0 queue[3] = D D
8√ 3 4 3
count = 3 + 1
0 count = 4
3 count = 4 back = 3
Continue…

48. enQueue Implementation Using Array(Circular)
From previous slide: front = 0, back = 3, count = 4
queue
front = 0
7 0
A
6 1
back = (3 + 1) % 8 B
back = 4 % 8
back = 4 C
5 2
0 queue[4] = E E D
8√ 4 4 3
count = 4 + 1
0 count = 5
4 count = 5 back = 4
Continue…

49. enQueue Implementation Using Array(Circular)
From previous slide: front = 0, back = 4, count = 5
queue
front = 0
7 0
A
6 1
back = (4 + 1) % 8 B
back = 5 % 8
back = 5 F C
5 2
0 queue[5] = F E D
8√ 5 back = 5 4 3
count = 5 + 1
0 count = 6
5 count = 6
Continue…

50. enQueue Implementation Using Array(Circular)
From previous slide: front = 0, back = 5, count = 6
queue
front = 0
back = 6 7 0
A
6 1
back = (5 + 1) % 8 G B
back = 6 % 8
back = 6 F C
5 2
0 queue[6] = G E D
8√ 6 4 3
count = 6 + 1
0 count = 7
6 count = 7
Continue…

51. enQueue Implementation Using Array(Circular)
From previous slide: front = 0, back = 6, count = 7
queue
back = 7 front = 0
7 0
H A
6 1
back = (6 + 1) % 8 G B
back = 7 % 8
back = 7 F C
5 2
0 queue[7] = H E D
8√ 7 4 3
count = 7 + 1
0 count = 8
7 count = 8
Continue…

52. deQueue Implementation Using Array(Circular)
void deQueue(){
cout<<"nt#### deQueue Circular ####n";
if(count == 0){
cout<<"ntQueue Circular Is Empty, No Data To Be Deleted!!!n";
}else{ queue
back = 7
queue[front] = NULL;
7 0
front=(front + 1) % max; H front = 1
6 1
count--; queue[0] = NULL G B
front = (0 + 1) % 8
front = 1 % 8 F C
} 5 2
0 front = 1 E D
} 8√ 1 4 3
count = 8 - 1
0 count = 7
1 count = 7
Continue…

53. deQueue Implementation Using Array(Circular)
From previous slide: front = 1, back = 7 , count = 7
queue
back = 7
7 0
H
6 1
queue[1] = NULL G
front = (1 + 1) % 8
front = 2% 8 F C
5 2
0 front = 2 E D front = 2
8√ 2 4 3
count = 7 - 1
0 count = 6
2 count = 6
Continue…

54. Queue Implementation Using Array(Circular)
void displayQueue(){
cout<<"nt#### Display Queue Circular ####n";
cout<<"ntfront:"<<front<<"t"<<"back:"<<back<<"tcount:"<<count<<“tmax:”<<max<<"n";
if(count == 0){
cout<<"ntQueue Circular Is Empty, No Data To Be Displayn";
}else{
cout<<"ntItem In Queue Circularn";
for(int i = 0; i < max; i++){
cout<<"t"<<queue[i];
}
}
}
Continue…

55. Queue Implementation Using Array(Circular)
int main(){
int selection;
menu:
cout<<"nnPlease Choose Your Selectionn";
cout<<"n1tenQueue Circularn";
cout<<"n2tdeQueue Circularn";
cout<<"n3tDisplay Queuen";
cout<<"ntSelection is:";
cin>>selection;
Continue…

56. Queue Implementation Using Array(Circular)
switch(selection){
case 1: enQueue();
displayQueue();
goto menu;
break;
case 2: deQueue();
displayQueue();
goto menu;
break;
case 3: displayQueue();
goto menu;
break;
Continue…

57. Queue Implementation Using Array(Circular)
default:cout<<"ntWrong Selectionn";
}
return 0;
}

58. 4.0 Queue Implementation Using
Linked List(Linear)

59. Queue Implementation Using Linked List(Linear)
Pointer-Based Implementation
• More straightforward than array-based
• Need Two external pointer (Front & Back) which front to
trace deQueue operation and back to trace deQueue
operation.

60. Create Queue Implementation Using Linked
List(Linear)
Example Code 1:
#include <iostream>
using namespace std;
struct nodeQueue{
char name;
int age; name age next
nodeQueue *next;
Compiler get the initial illustrated structure of node
};
Continue…

61. Create Queue Implementation Using Linked
List(Linear)
nodeQueue *back_ptr = NULL; NULL
nodeQueue *front_ptr=NULL; back_ptr
NULL
front_ptr
Continue…

62. enQueue Implementation Using Linked
List(Linear)
void enQueue(){
0110
//create new node
0110 Ali 29 NULL
nodeQueue *newnode;
newnode
newnode = new nodeQueue;
cout<<"nt####enQueue####n";
//assign data field for name and age
cout<<"Enter Name:";
cin>>newnode->name;
cout<<"Enter Age:";
cin>>newnode->age;
newnode->next = NULL;
Continue…

63. enQueue Implementation Using Linked
List(Linear)
//insert newnode into queue Insertion to an empty queue
//check whether queue is empty
if((front_ptr == NULL) && (back_ptr == NULL)){ 0110
front_ptr = newnode; 0110 Ali 29 NULL
back_ptr = newnode; newnode name age next
}else{ 0110
0110
back_ptr->next = newnode; front_ptr
back_ptr
back_ptr = newnode;
}
Continue…

64. enQueue Implementation Using Linked
Insertion to a non empty queue
List(Linear)
0111
0111 Tina 30 NULL
newnode name age next
0110
0110 Ali 29 NULL 0110
front_ptr back_ptr
name age next
back_ptr->next = newnode;
back_ptr=newnode;
Continue…

65. enQueue Implementation Using Linked
List(Linear)
Insertion to a non empty queue
0110 0111
0110 Ali 29 0111 Tina 30 NULL 0111
front_ptr back_ptr
name age next name age next
Continue…

66. deQueue Implementation Using Linked List(Linear)
Continue…

67. void deQueue(){
cout<<"nt####deQueue####n";
//check whether queue is empty
if((front_ptr == NULL) && (back_ptr == NULL)){
cout<<"ntQueue Is Empty!!!n";
}else{
nodeQueue *temp;
temp = front_ptr;
if(front_ptr->next == NULL){
front_ptr = NULL;
back_ptr = NULL; If the queue contains one item only
delete temp;
}else{
front_ptr = front_ptr->next;
delete temp; } } }
Continue…

68. deQueue Implementation Using Linked List(Linear)
If the queue contains one item only to be deleted
nodeQueue *temp;
temp = front_ptr;
0110
0110 Ali 29 NULL 0110
front_ptr back_ptr
name age next
0110
if(front_ptr->next == NULL){
temp
front_ptr = NULL; NULL NULL
back_ptr = NULL; front_ptr back_ptr
delete temp;
}else{
…}
Continue…

69. deQueue Implementation Using Linked
List(Linear)
If the queue contains more than one item
nodeQueue *temp;
temp = front_ptr;
0110 0111
0110 Ali 29 0111 Tina 30 NULL 0111
front_ptr name age next name age next back_ptr
0110
temp
Continue…

70. …}else{
front_ptr = front_ptr->next;
delete temp; }
0110 0111
0111 Ali 29 0111 Tina 30 NULL 0111
front_ptr name age next name age next back_ptr
0110
temp
0111
0111 Tina 30 NULL 0111
front_ptr name age next back_ptr
Continue…

71. displayQueue Implementation Using Linked
List(Linear)
void displayQueue(){
cout<<"nt####Display Queue####n";
if((front_ptr == NULL) && (back_ptr == NULL)){
cout<<"ntQueue Is Empty!!!n";
cout<<"ntfront_ptr :"<<front_ptr<<"tback_ptr :"<<back_ptr<<endl;
}else{
nodeQueue *cursor;
cursor=front_ptr;
cout<<"ntThe Elements In Queue Aren";
cout<<"ntfront_ptr :"<<front_ptr<<"tback_ptr :"<<back_ptr<<endl;
int node=1;
while(cursor){
cout<<"ntNode :"<<node++<<"tName :"<<cursor->name<<"tAge :"<<cursor-
>age<<"tcursor-next:"<<cursor->next<<endl;
cursor=cursor->next; } } Continue…

72. Queue Implementation Using Linked List(Linear)
int main()
{
int selection;
menu:
cout<<"nnMenu Selectionn";
cout<<"n1tenQueuen";
cout<<"n2tdeQueuen";
cout<<"n3tDisplay Queuen";
cout<<"ntSelection is:";
cin>>selection;
Continue…

73. Queue Implementation Using Linked List(Linear)
switch(selection){
case 1: enQueue();
displayQueue();
goto menu;
break;
case 2: deQueue();
displayQueue();
goto menu;
break;
case 3: displayQueue();
goto menu;
break;
default:cout<<"ntWrong Selectionn"; }
return 0;
}
Continue…