Stack. The Stack stores arbitrary objects Insertions and deletions follow the last-in firstout

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Stack The Stack stores arbitrary objects Insertions and deletions follow the last-in firstout scheme Think of a spring-loaded plate dispenser Main stack operations: push(element elm): inserts an

1 Stack The Stack stores arbitrary objects Insertions and deletions follow the last-in firstout scheme Think of a spring-loaded plate dispenser Main stack operations: push(element elm): inserts an element Element pop(): removes the last inserted element Auxiliary stack operations: Element top(): returns the last inserted element without removing it integer size(): returns the number of elements stored boolean empty(): indicates whether no elements are stored 9-32

2 Applications of Stacks Direct applications Page-visited history in a Web browser (e.g., keeping recently visited web site URLs) Undo sequence in a text editor Chain of method calls in the C++ run-time system Indirect applications Auxiliary data structure for algorithms Stack is used as a component of other data structures 9-33

3 Array 기반의 Stack 구현 /* Stack with Array (1) */ #include <stdio.h> #include <stdlib.h> typedef int Elm_t; typedef struct stack Elm_t *pbuffer; int max_size; int stacktop; Stack; int initstack(stack *ps, int size); void pushstack(stack *ps, Elm_t data); Elm_t popstack(stack *ps); void printstack(stack *ps); void main() Stack stack; initstack(&stack, 10); printf("after initialization of stack n"); printstack(&stack); /* Stack with Array (2) */ 9-34 for (int i = 0; i < 10; i++) pushstack(&stack, i); printf("push (%2d) n", i); printstack(&stack); for (int i = 0; i < 10; i++) data = popstack(&stack); printf("pop (%2d) n", data); printstack(&stack); int initstack(stack *ps, int size) ps->max_size = size; ps->stacktop = -1; ps->pbuffer = (Elm_t*)malloc(sizeof(Elm_t)* size); if (ps->pbuffer == NULL) return -1; else return size;

4 /* Stack with Array (3) */ void pushstack(stack *ps, Elm_t data) if (ps->stacktop >= ps->max_size) printf("exception::stack is Full!! - no push operation n"); return; ps->stacktop++; ps->pbuffer[ps->stacktop] = data; Elm_t popstack(stack *ps) if (ps->stacktop < 0) printf("exception::stack is Empty!! - no pop operation n"); return -1; data = ps->pbuffer[ps->stacktop]; ps->stacktop--; return data; 9-35

5 /* Stack with Array (4) */ void printstack(stack *ps) if (ps->stacktop < 0) printf("exception::stack is Empty!! n"); return; printf("current stack (size: %2d) : ", ps->stacktop + 1); for (int i = ps->stacktop; i >= 0; i--) data = ps->pbuffer[i]; printf("%d, ", data); printf(" n"); 9-36

6 Linked List 기반의 Stack 구현 /* Stack based on Linked List (1) */ #include <stdio.h> #include <stdlib.h> typedef int Elm_t; typedef struct listnode struct listnode *prev; struct listnode *next; ListNode; typedef struct liststack ListNode *stacktop; int size; ListStack; void initstack(liststack *ps, int size); void pushstack(liststack *ps, Elm_t data); Elm_t popstack(liststack *ps); void printstack(liststack *ps); /* Stack based on Linked List (2) */ void main() ListStack stack; initstack(&stack, 10); printf("after initialization of stack n"); printstack(&stack); for (int i = 0; i < 10; i++) pushstack(&stack, i); printf("push (%2d) n", i); printstack(&stack); for (int i = 0; i < 10; i++) data = popstack(&stack); printf("pop (%2d) n", data); printstack(&stack); 9-37

7 /* Stack based on Linked List (3) */ void initstack(liststack *ps, int size) ps->stacktop = NULL; ps->size = 0; void pushstack(liststack *ps, Elm_t data) ListNode *pnewln; pnewln = (ListNode *)malloc(sizeof(listnode)); pnewln->data = data; pnewln->prev = NULL; if (ps->size == 0) ps->stacktop = pnewln; ps->stacktop->next = NULL; else pnewln->next = ps->stacktop; ps->stacktop->prev = pnewln; ps->stacktop = pnewln; ps->size++; /* Stack based on Linked List (4) */ Elm_t popstack(liststack *ps) if (ps->size <= 0) printf("exception::stack is Empty!! no pop operation n"); return -1; data = ps->stacktop->data; ListNode *pln = ps->stacktop; ps->stacktop = ps->stacktop->next; if (ps->stacktop!= NULL) // when the last //ListNode is deleted, skip next statement ps->stacktop->prev = NULL; ps->size--; free(pln); return data; 9-38

8 /* Stack based on Linked List (5) */ void printstack(liststack *ps) if (ps->size <= 0) printf("exception::stack is Empty!! n"); return; printf("current stack (size: %2d) : ", ps->size); ListNode *pln = ps->stacktop; for (int i = 0; i < ps->size; i++) data = pln->data; printf("%d, ", data); pln = pln->next; printf(" n"); 9-39

9 Queues The Queue stores arbitrary objects Insertions and deletions follow the first-in first-out (FIFO) scheme Insertions are at the rear of the queue and removals are at the front of the queue Main queue operations: enqueue(object): inserts an element at the end of the queue dequeue(): removes the element at the front of the queue Auxiliary queue operations: object front(): returns the element at the front without removing it integer size(): returns the number of elements stored boolean empty(): indicates whether no elements are stored Exceptions Attempting the execution of dequeue or front on an empty queue throws an QueueEmpty 9-40

10 Array 기반의 Queue 구현 /* Queue based on Array (1) */ #include <stdio.h> #include <stdlib.h> typedef int Elm_t; typedef struct Queue Elm_t *pbuffer; int max_size; int front; int end; int size; Queue; int initqueue(queue *pq, int size); void enqueue(queue *pq, Elm_t data); Elm_t dequeue(queue *pq); void printqueue(queue *pq); void main() Queue queue; initqueue(&queue, 10); printf("after initialization of queue n"); Yeungnam printqueue(&queue); University (yuantl) /* Queue based on Array (2) */ for (int i = 0; i < 10; i++) enqueue(&queue, i); printf("enqueue (%2d) n", i); printqueue(&queue); for (int i = 0; i < 10; i++) data = dequeue(&queue); printf("dequeue (%2d) n", data); printqueue(&queue); int initqueue(queue *pq, int Qsize) pq->max_size = Qsize; pq->size = 0; pq->front = pq->end = 0; pq->pbuffer = (Elm_t*)malloc(sizeof(Elm_t)* Qsize); if (pq->pbuffer == NULL) return -1; else return Qsize; 9-41

11 /* Queue based on Array (3) */ void enqueue(queue *pq, Elm_t data) if (pq->size >= pq->max_size) printf("exception::queue is Full!! - no enque operation n"); return; pq->pbuffer[pq->end] = data; pq->size++; pq->end = (pq->end + 1) % pq->max_size; // circular queue Elm_t dequeue(queue *pq) if (pq->size <= 0) printf("exception::queue is Empty!! - no deque operation n"); return -1; data = pq->pbuffer[pq->front]; pq->size--; pq->front = (pq->front+1) % pq->max_size; return data; 9-42

12 /* Queue based on Array (4) */ void printqueue(queue *pq) if (pq->size <= 0) printf("exception::queue is Empty!! n"); return; printf("current queue (size: %2d) : ", pq->size); int j = pq->front; for (int i = 0; i < pq->size; i++) data = pq->pbuffer[j]; printf("%d, ", data); j = (j + 1) % pq->max_size; printf(" n"); 9-43

13 /* Queue based on Linked List (1) */ #include <stdio.h> #include <stdlib.h> typedef int Elm_t; typedef struct listnode struct listnode *prev; struct listnode *next; ListNode; typedef struct ListQueue ListNode *front; ListNode *end; int size; ListQueue; Linked List 기반의 Queue 구현 void initqueue(listqueue *pq); void enqueue(listqueue *pq, Elm_t data); Elm_t dequeue(listqueue *pq); void printqueue(listqueue *pq); 9-44 /* Queue based on Linked List (2) */ void main() ListQueue queue; initqueue(&queue); printf("after initialization of queue n"); printqueue(&queue); for (int i = 0; i < 10; i++) enqueue(&queue, i); printf("enqueue (%2d) n", i); printqueue(&queue); for (int i = 0; i < 10; i++) data = dequeue(&queue); printf("dequeue (%2d) n", data); printqueue(&queue); void initqueue(listqueue *pq) pq->size = 0; pq->front = pq->end = NULL;

14 /* Queue based on Linked List (3) */ void enqueue(listqueue *pq, Elm_t data) ListNode *pnewln; pnewln = (ListNode *)malloc(sizeof(listnode)); pnewln->data = data; pnewln->next = NULL; if (pq->size == 0) pnewln->prev = NULL; pq->front = pq->end = pnewln; else pnewln->prev = pq->end; pq->end->next = pnewln; pq->end = pnewln; pq->size++; /* Queue based on Linked List (4) */ Elm_t dequeue(listqueue *pq) if (pq->size <= 0) printf("exception::queue is Empty!! - no deque operation n"); return -1; data = pq->front->data; pq->size--; ListNode *pln = pq->front; pq->front = pq->front->next; free(pln); return data; 9-45

15 /* Queue based on Linked List (5) */ void printqueue(listqueue *pq) if (pq->size <= 0) printf("exception::queue is Empty!! n"); return; printf("current queue (size: %2d) : ", pq->size); ListNode *pln = pq->front; for (int i = 0; i < pq->size; i++) data = pln->data; printf("%d, ", data); pln = pln->next; printf(" n"); 9-46

16 Queue 의응용 (1) 패킷통신시스템의큐 패킷데이터통신시스템에서의입력 / 출력 Queue queue: first come, first served put (insert) a newly arrived packet in the tail of the queue ge the packet at the head of the queue remove (delete) the acknowledged packet from the queue Packet Queue Packet input (insert at tail) Packet transmit (get/remove from head) 9-47

17 Queue 의응용 (2) - Round Robin Schedulers We can implement a round robin scheduler using a queue Q by repeatedly performing the following steps: 1. e = Q.front(); Q.dequeue() 2. Service element e 3. Q.enqueue(e) Queue Dequeue Enqueue Shared Service 9-48

18 Homework 연결리스트를이용한 Galaxy 구현 (1) 구조체 struct Star 는데이터멤버 (data members) 로 string starname, int starid, double distance, double luminosity, double mass, double radius, int age 과함께이중연결리스트구성을위한두개의포인터 (Star *pprev, Star *pnext) 를가진다. starid 는중복되지않는값으로지정되어야한다. (2) 구조체 struct Galaxy 는데이터멤버로 string glxyname, int numstar 과함께 Star 구조체의이중연결리스트를가리키기위한두개의포인터 (Star *pfirst, Star *plast) 를가진다. 이구조체 struct Galaxy 를사용하는함수는다음과같다 : Star * genstar(int id) : 하나의 star 를동적으로생성하며, star 의데이터멤버들을랜덤함수를사용하여임의의값으로초기화한후, 생성된 star 의주소를반환한다. starid 는중복되지않는값으로 e 전달되는값을사용하여야하며, starname 은알파벳 a ~ z 5 ~ 10 자로구성된다. 데이터멤버 distance, luminosity, mass, radius 및 age 는 10.0 ~ 범위의값을임의로가진다. printgalaxy(galaxy *pglx) : 이중연결리스트로구성된 Galaxy 에포함된 star 들의 starname, stari d 를순서대로 ( 첫번째 (head) 노드부터마지막 (tail) 노드까지 ) 출력한다. insertnodeattail(galaxy *pglx, Star *ps) : 하나의 star 를이중연결리스트의마지막위치 (tail) 에추가한다. insertnodeinorder(galaxy *pglx, Star *ps) : 하나의 star 를이중연결리스트의 starid 의오름차순순서에맞는위치에삽입한다. Star *getfromhead(galaxy *pglx) : 이중연결리스트의맨처음노드의주소값을반환한다. 이연산에서는헤더노드를삭제하지는않는다. Star *removefromhead(galaxy *pglx) : 이중연결리스트의맨처음노드 (head) 를삭제한다. (3) 각구조체정의는별도의헤더파일에구현되어야한다 : MyStar.h, MyGalaxy.h. 9-49

19 (4) 다음내용을포함하는 main() 함수를사용할것 : // Standard comments for source code #include MyStar.h #include MyGalaxy.h... #define NUM_STARS void main() Galaxy *pglx; Star *pnew; int *starid; pglx = (Galaxy *) malloc(sizeof(galaxy)); pglx->pfirst = NULL; pglx->plast = NULL; pglx->numstar = 0; starid = (int *)malloc(sizeof(int) * NUM_STARS); genbigrandarray(starid, NUM_STARS); for (int i=0; i<num_stars; i++) pnew = genstar(starid[i]); insertnodeinorder(pglx, pnew); printf( Galaxy after insertnodeinorder(id: %d) n, ps->id); printgalaxy(pglx); 9-50

20 for (i=0; i<num_stars; i++) ps = removefromhead(pglx); if (ps!= NULL) printf(" Node (id: %d) removed from list head n, ps->id); printf( Galaxy after node remove from head: n ); printgalaxy(pglx); free(ps); ps = getfromhead(pglx); if (ps!= NULL) printf(" New head in list of Galaxy: %d n, ps->id); free (pglx); 9-51

Queues. A queue is a special type of structure that can be used to maintain data in an organized way.

Queues. A queue is a special type of structure that can be used to maintain data in an organized way. A queue is a special type of structure that can be used to maintain data in an organized way. This data structure is commonly implemented in one of two ways: as an array or as a linked list. In either