Stack & Queue on Self-Referencing Structures

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1 PDS: CS Computer Sc & Engg: IIT Kharagpur 1 Stack & Queue on Self-Referencing Structures

2 PDS: CS Computer Sc & Engg: IIT Kharagpur 2 Representation of Stack struct stack { int data ; struct stack *next ; ; typedef struct stacknode node, *stack ;

3 PDS: CS Computer Sc & Engg: IIT Kharagpur 3 stack s Data Area Dynamically Created

4 PDS: CS Computer Sc & Engg: IIT Kharagpur 4 Empty Stack stack s Empty Stack

5 PDS: CS Computer Sc & Engg: IIT Kharagpur 5 Push stack s Push

6 PDS: CS Computer Sc & Engg: IIT Kharagpur 6 Pop stack s 20 Pop

7 PDS: CS Computer Sc & Engg: IIT Kharagpur 7 Interface File: stacksr.h #ifndef _STACKSR_H #define _STACKSR_H #include <stdio.h> #include <stdlib.h> #define ERROR 1 #define OK 0 struct stack { // stacksr.h int data ; struct stack *next ; ;

8 PDS: CS Computer Sc & Engg: IIT Kharagpur 8 typedef struct stack node, *stack ; #define INIT(s) ((s)=null) #define ISEMPTY(s) ((s) == NULL) int push(stack *, int) ; int pop(stack *) ; int top(stack, int *) ; #endif

9 PDS: CS Computer Sc & Engg: IIT Kharagpur 9 Note We macro define INIT and ISEMPTY as the code is very simple. We also could have done inline function.

10 PDS: CS Computer Sc & Engg: IIT Kharagpur 10 Implementation File: stacksr.c #include "stacksr.h" int push(stack *s, int n) { // stacksr.c stack temp ; temp=(stack)malloc(sizeof(node)) ; if(temp == NULL) { printf("the STACK is full\n"); return ERROR ; temp->data=n; temp->next=*s ; *s = temp ;

11 PDS: CS Computer Sc & Engg: IIT Kharagpur 11 return OK ; int pop(stack *s) { stack temp ; if(isempty(*s)) { printf("the STACK is empty\n"); return ERROR ; temp=*s; *s=(*s)->next ; free(temp) ; return OK ;

12 PDS: CS Computer Sc & Engg: IIT Kharagpur 12 int top(stack s, int *val) { if(isempty(s)) { printf("the STACK is empty\n") ; return ERROR ; *val = s -> data ; return OK ;

13 PDS: CS Computer Sc & Engg: IIT Kharagpur 13 User Program: teststacksr.c #include <stdio.h> #include "stacksr.h" int main() // teststacksr.c { stack s ; int x, err, val ; char c ; INIT(s); printf(" U for push (U 15)\n O for pop\n T for to printf(" E for exit :\n");

14 PDS: CS Computer Sc & Engg: IIT Kharagpur 14 while((c = getchar())!= e && c!= E ) switch(c) { case u : case U : scanf("%d",&x); err = push(&s,x); break; case o : case O : err = pop(&s); break; case t : case T : err = top(s, &val) ;

15 PDS: CS Computer Sc & Engg: IIT Kharagpur 15 case \n : case \t : case : default : return 0; if(!err) printf("%d\n", val); break; break; printf("token Unknown\n");

16 PDS: CS Computer Sc & Engg: IIT Kharagpur 16 Representation of Queue struct queue { int data ; struct queue *next ; ; typedef struct { struct queue *front, *rear ; queue ;

17 PDS: CS Computer Sc & Engg: IIT Kharagpur 17 Note We use a dummy node. In an empty queue, both the front and the rear pointers points to the dummy node.

18 PDS: CS Computer Sc & Engg: IIT Kharagpur 18 queue s Dummy Node front rear Empty Queue

19 PDS: CS Computer Sc & Engg: IIT Kharagpur 19 Dummy Node queue s front rear Dynamically Created Data Area

20 PDS: CS Computer Sc & Engg: IIT Kharagpur 20 Dummy Node queue s front rear Add

21 PDS: CS Computer Sc & Engg: IIT Kharagpur 21 Delete Dummy Node queue s front rear New Dummy Node

22 PDS: CS Computer Sc & Engg: IIT Kharagpur 22 Interface File: queuesr.h #ifndef _QUEUESR_H #define _QUEUESR_H #include <stdio.h> #include <stdlib.h> #define ERROR 1 #define OK 0 struct queue { // queuesr.h int data ; struct queue *next ; ;

23 PDS: CS Computer Sc & Engg: IIT Kharagpur 23 typedef struct queue node; typedef struct { struct queue *front, *rear ; queue ; #define ISEMPTY(q) ((q).front == (q).rear) void init(queue *) ; int add(queue *, int) ; int delete(queue *); int front(queue, int *) ; #endif

24 PDS: CS Computer Sc & Engg: IIT Kharagpur 24 Implementation File: queuesr.c #include "queuesr.h" void init(queue *qp) { // queuesr.c node *temp ; temp = (node *)malloc(sizeof(node)) ; qp->front=qp->rear=temp ; int add(queue *qp, int n) { node *temp ; temp=(node *)malloc(sizeof(node)) ; if(temp == NULL) return ERROR ;

25 PDS: CS Computer Sc & Engg: IIT Kharagpur 25 temp->data=n; qp->rear->next=temp ; qp->rear = temp ; return OK ; int front(queue q, int *v) { if(isempty(q)) return ERROR ; *v= q.front->next->data ; return OK ; int delete(queue *qp) { node *temp ;

26 PDS: CS Computer Sc & Engg: IIT Kharagpur 26 if(isempty(*qp)) return ERROR ; temp = qp->front ; qp->front=qp->front->next ; free(temp) ; return OK ;

27 PDS: CS Computer Sc & Engg: IIT Kharagpur 27 User Program: testqueuesr.c #include <stdio.h> #include "queuesr.h" int main() // testqueuesr.c { queue q ; int x, err, val ; char c; init(&q); printf(" A for add (A 15)\n") ; printf(" D for delete\n F for front\n E for exit while((c = getchar())!= e && c!= E )

28 PDS: CS Computer Sc & Engg: IIT Kharagpur 28 switch(c) { case a : case A : scanf("%d",&x); err = add(&q,x); if(err) printf("the Queue is full\n") ; break; case d : case D : err = delete(&q); if(err) printf("the Queue is empty\n") ; break;

29 PDS: CS Computer Sc & Engg: IIT Kharagpur 29 case f : case F : break; err = front(q, &val) ; if(err) printf("the Queue is empty\n") ; else printf("%d\n",val); case \n : case \t : case : break; default : printf("token Unknown\n");

30 PDS: CS Computer Sc & Engg: IIT Kharagpur 30 return 0;

31 PDS: CS Computer Sc & Engg: IIT Kharagpur 31 Union Type So far all our data are of single type. But it is possible to have data of any one of a few different types e.g. either of type int or of type double. The C language provides support to have data of type union.

32 PDS: CS Computer Sc & Engg: IIT Kharagpur 32 Union Type: an Example typedef union data { int datai; double datad; intdouble; A variable of type union data or intdouble can store either a value of type int or of type double. The allocated space is large enough to accomodate the data of the largest size. The fields are accessed like a structure.

33 PDS: CS Computer Sc & Engg: IIT Kharagpur 33 Note It is necessary to attach a tag to remember the type of the actual data present. We consider a stack of type intdouble.

34 PDS: CS Computer Sc & Engg: IIT Kharagpur 34 Interface File: stacku.h #ifndef _STACKU_H #define _STACKU_H #include <stdio.h> #include <stdlib.h> #define ERROR 1 #define OK 0 typedef struct { // stacku.h union data { int I; double D;

35 PDS: CS Computer Sc & Engg: IIT Kharagpur 35 data ; char type; intdouble; struct stack { intdouble data ; struct stack *next ; ; typedef struct stack node, *stack ; #define INIT(s) ((s)=null) #define ISEMPTY(s) ((s) == NULL) int push(stack *, intdouble) ; int pop(stack *) ;

36 PDS: CS Computer Sc & Engg: IIT Kharagpur 36 int top(stack, intdouble *) ; #endif

37 PDS: CS Computer Sc & Engg: IIT Kharagpur 37 Implementation File: stacku.c #include "stacku.h" int push(stack *s, intdouble n) { // stacku.c stack temp ; temp=(stack)malloc(sizeof(node)) ; if(temp == NULL) { printf("the STACK is full\n"); return ERROR ; temp->data = n; temp->next=*s ;

38 PDS: CS Computer Sc & Engg: IIT Kharagpur 38 *s = temp ; return OK ; int pop(stack *s) { stack temp ; if(isempty(*s)) { printf("the STACK is empty\n"); return ERROR ; temp=*s; *s=(*s)->next ; free(temp) ; return OK ;

39 PDS: CS Computer Sc & Engg: IIT Kharagpur 39 int top(stack s, intdouble *val) { if(isempty(s)) { printf("the STACK is empty\n") ; return ERROR ; *val = s -> data; return OK ;

40 PDS: CS Computer Sc & Engg: IIT Kharagpur 40 User Program: teststacku.c #include <stdio.h> #include "stacku.h" int main() // teststacku.c { stack s ; int err ; intdouble d; char c ; INIT(s); printf(" Ui for push int (Ui 15)\n Uf for push floa

41 PDS: CS Computer Sc & Engg: IIT Kharagpur 41 printf(" O for pop\n T for top \n E for exit :\n" while((c = getchar())!= e && c!= E ) switch(c) { case u : case U : scanf("%c", &c); if(c == i c == I ) { scanf("%d",&d.data.i); d.type = i ; else if(c == f c == F ) { scanf("%lf",&d.data.d); d.type = f ;

42 PDS: CS Computer Sc & Engg: IIT Kharagpur 42 case o : case O : case t : case T : err = push(&s,d); break; err = pop(&s); break; err = top(s, &d) ; if(!err) { if(d.type == i ) printf("%d\n", d.d if(d.type == f ) printf("%f\n", d.d break;

43 PDS: CS Computer Sc & Engg: IIT Kharagpur 43 case \n : case \t : case : default : return 0; break; printf("token Unknown\n");

Stack & Queue on Self-Referencing Structures

C Programming 1 Stack & Queue on Self-Referencing Structures C Programming 2 Representation of Stack struct stack { int data ; struct stack *next ; ; typedef struct stacknode node, *stack ; C Programming