c program day-18

7/31/2019 C Program Day-18

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QUEUE :

It is a non-primitive, linear data structure, and a subclass of list data structure.

It is an ordered, homogeneous collection of elements in which elements areappended at one end called REAR end, and elements are deleted at other end called

FRONT end.

It follows First-in First-Out mechanism, in which elements comes first will be

removed first.

Two operation are frequently carried on queue. They are insertion and deletion.

The insertion operation is possible only when the queue contains elements less

than the capacity it can hold.The deletion is possible when the queue contains at least one element.


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Disadvantages of simple Queue :

If more elements are deleted, the value of front will be increased, and as a result beginning

portion of queue will be empty. Therefore, if we try to insert a new element, no element is

inserted, because new element are always inserted from the rear and if the last location of

queue holds an element, even though space is available at the beginning of queue, no element

will be inserted. The queue will be treated as Overflow

Queue using Pointer :Pointer implementation of a Queue can be carried out is similar to array

implementation. This Dynamic Implementation, create NODE at run time, accordingly Insertion,Deletion operation can be done.

(i) creating a Queue

(ii) Checking Queue either full or empty(iii) Initializing a Queue

(iv) Insert an element into the Queue

(v) Delete an element from the Queue.

(vi) Display elements of Queue.


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Types of Queues :

The major disadvantage of queue is, when the rearpointer reaches to the end of the queue (array), no more

elements can be added in the queue, even if the beginning

memory locations of array are empty. To Overcome the above

disadvantage, different types of Queue can be applied.

(i) Circular Queue

(ii) DEQueue (Double Ended Queue)

(iii) Priority Queue


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# include # include

struct queue{int items[100];int front,rear;};

struct queue q;int givendata,rdata,n;

empty(){return((q.front == q.rear) ? 1 : 0);

}

void rem(){if (empty() == 1)

printf("underflow");Continued,


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else{if (q.front == 99)

q.front = 0;else

(q.front)++;rdata = q.items[q.front];printf("\n Data removed is %d",rdata);}

}void show(){int i,x;

if (empty() == 1)printf("\n queue empty");

elsex = ((q.front== 99)? -1:q.front);for ( i = q.rear ; i > x ;i--)

printf("%d-->",q.items[i]);}

void insert(){ Continued,


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if (q.rear == 99)q.rear = 0;

else(q.rear)++;

if (q.rear == q.front)printf("overflow");else

q.items[q.rear] = givendata;}

void main(){q.front = q.rear = 99;do{printf("\n Queue Operations ");printf("\n 1.Insert item");printf("\n 2.Remove item");printf("\n 3.Show items in Queue ");printf("\n 4.Quit");

printf("\n Enter your choice : ");Continued,


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scanf("%d",&n);

switch(n)

{case 1:printf("\nEnter integer data : ");scanf("%d",&givendata);insert();break;

case 2:rem();break;

case 3:show();break;

}}while (n != 4);}


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# include # include

#define null 0

struct list{int info;struct list *next;};

typedef struct list node;node *front,*rear;

void insert()

{int i;node *new;new = (node *)malloc(sizeof(node));printf("\nEnter integer data :");

scanf("%d",&i);Continued,


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new->next = null;new->info = i;if (front == null)

{front = new;rear = new;

}else

{rear->next = new;rear = new;

}}void delete(){

node *temp;if (front!= null){

temp = front;front = front->next;

free(temp);}} Continued,


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void display(){

node *temp;temp = front;while (temp){

printf("%d-->",temp->info);temp = temp->next;

}}void main(){int ch;front = null;rear = null;

do{printf("\n 1. Insert");printf("\n 2. Delete");printf("\n 3. Display");printf("\n 4. Exit");printf("\n Enter your choice : ");

Continued,


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scanf("%d",&ch);switch(ch){case 1:

insert();break;

case 2:delete();break;

case 3:display();break;

}}while(ch != 4);

}


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Session Summary

The stack is an ordered collection of elements in which insertions and deletions arerestricted to one end.

PUSH is an operation used to add a new element into a stack

POP is an operation used to remove the top most element from the stack

An queue is an ordered collection of elements in which insertions are made is referred

as the rear end and the end from which deletions are made is referred as front end.

The primitive operations that can be carried out in a queue are enqueue and dequeue

operations

The enqueue is an operation used to add a new element into the rear end of a queue

The dequeue is an operation used to remove an element from the front end of a queue


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EXERCISES

1. State the difference between stack & Linked list?

2. State the difference between Queue & Linked List?

3. Explain in detail the Push and Pop operation in a stack?

4. Explain in detail the Enqueue and Dequeue operation in a Queue?

5. Explain in brief the methods to check whether the stack is empty or not?

6. Explain in brief the methods to check whether the queue is full or not?

c program day-18

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