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# Notes DATA STRUCTURE - queue

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nota queue dari subjek data structure dah diringkaskan | PSMZA .

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### Notes DATA STRUCTURE - queue

1. 1. QUEUE
2. 2. Course ObjectivesAt 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. 3. 1.0 Introduction to Queue
4. 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. 5. Introduction to Queue• Important in simulation & analyzing the behavior of complex systems
6. 6. Queue Applications• Real-World Applications – Cashier lines in any store – Check out at a bookstore – Bank / ATM – Call an airline
7. 7. Queue Applications• Computer Science Applications – Print lines of a document – Printer sharing between computers – Recognizing palindromes – Shared resource usage (CPU, memory access, …)
8. 8. Queue Applications• Simulation – A study to see how to reduce the wait involved in an application
9. 9. Queue implementationRemove/ Add/ A B C EnqueueDequeue Front/Head Back/Rear Basic Structure of a Queue: •Data structure that hold the queue •head •rear
10. 10. Queue implementation Add/ A B C D Enqueue Head Rear Insert D into Queue (enQueue) : D is inserted at rearRemove/Dequeue A B C D Head Rear Delete from Queue (deQueue) : A is removed
11. 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. 12. Queue ImplementationImplementation: – Array-based (Linear or Circular) – Pointer-based : Link list (Linear or Circular)
13. 13. 2.0 Queue Implementation Using Array(Linear)
14. 14. Queue Implementation UsingArray(Linear)• Number of elements in Queue are fixed during declaration.• Need isFull() operation to determine whether a queue is full or not.
15. 15. Queue Implementation Using Array(Linear)• Queue structure need at least 3 elements:1) Element to store items in Queue2) Element to store index at head3) Element to store index at rear
16. 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 -1front back
17. 17. Create Queue operationExample Code 1#include <iostream>using namespace std;#define max 5int front = 0, back = -1; Create Queuechar item[max], newitem; item 0 0 1 2 3 4 -1 front back Front refer to index 0 Continue…
18. 18. enQueue operationvoid 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. 19. enQueue operation item back++ 0 0 1 2 3 4 1 front A B back back = 0 +1 back = 1Front 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 +1Front refer to index 0 back = 2 From back/rear item[back] = newitem Continue…
20. 20. enQueue operation item back++ 0 0 1 2 3 4 3 front A B C D back back = 2 +1 back = 3Front 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 = 4Front refer to index 0 From back/rear item[back] = newitem Continue…
21. 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 + 1itemdeleted = item[front] Front refer to index 0 back = 4front = 0 From front/head item[front] = NULL Continue…
22. 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 = 4itemdeleted = item[front] From front/headfront = 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. 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/headitemdeleted = item[front] item[front] = NULLfront = 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. 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 = 4itemdeleted = item[front] From front/headfront = 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. 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 = 4itemdeleted = item[front] From front/headfront = 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. 26. Retrieve at front(getFront) operationvoid 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. 27. Retrieve at back(getRear) operationvoid 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. 28. destroyQueue operationvoid destroyQueue(){ delete [] item;} Continue…
29. 29. displayQueue operationvoid 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. 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. 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. 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. 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 backfront = 4 + back = 3 + 11 back = 4front = 5
34. 34. Queue Implementation Using Array(Linear)• Rightward drifting solutions – Shift array elements after each deletion • Shifting dominates the cost of the implementation
35. 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 cant be used to distinguish between queue-full & queue- empty conditions
36. 36. Queue Implementation Using Array(Linear) • Solution: – Use a counter – Count == 0 means empty queue – Count == MAX_QUEUE means full queue
37. 37. 3.0 Queue Implementation Using Array(Circular)
38. 38. Queue Implementation UsingArray(Circular)• Number of elements in Queue are fixed during declaration.• Need isFull() operation to determine whether a queue is full or not.
39. 39. Queue Implementation Using Array(Circular)• Queue structure need at least 3 elements:1) Element to store items in Queue2) Element to store index at head3) Element to store index at rear4) Element to store index in counter
40. 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. 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. 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. 43. Queue Implementation Using Array(Circular)Example Code 2: queue#include <iostream> front = 0using namespace std; 7 0 6 1#define max 8char queue[max], newitem; 5 2int front = 0, back = -1, count = 0; 4 3 back = -1 count = 0 Continue…
44. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 57. Queue Implementation Using Array(Circular)default:cout<<"ntWrong Selectionn"; }return 0;}
58. 58. 4.0 Queue Implementation Using Linked List(Linear)
59. 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. 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. 61. Create Queue Implementation Using Linked List(Linear)nodeQueue *back_ptr = NULL; NULLnodeQueue *front_ptr=NULL; back_ptr NULL front_ptr Continue…
62. 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. 63. enQueue Implementation Using Linked List(Linear)//insert newnode into queue Insertion to an empty queue//check whether queue is emptyif((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. 64. enQueue Implementation Using LinkedInsertion 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. 65. enQueue Implementation Using Linked List(Linear) Insertion to a non empty queue 0110 0111 0110 Ali 29 0111 Tina 30 NULL 0111front_ptr back_ptr name age next name age next Continue…
66. 66. deQueue Implementation Using Linked List(Linear) Continue…
67. 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. 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. 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 0111front_ptr name age next name age next back_ptr 0110 temp Continue…
70. 70. …}else{front_ptr = front_ptr->next;delete temp; } 0110 0111 0111 Ali 29 0111 Tina 30 NULL 0111front_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. 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. 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. 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…