Queue Using Single Pointer Linked List

#include <stdio.h>

#include<stdlib.h>

#include<math.h>

#define size 5

int top=-1;

void enque(void);

void deque(void);

void peek(void);

void isEmpty(void);

void isFull(void);

void display(void);

struct queue{

int data;

struct node *next;

};

struct queue *head=0;

void main() {

int c,e;

do{

switch(c)

{

case 1:

enque();

break;

case 2:

deque();

break;

case 3:

peek();

break;

case 4:

isEmpty();

break;

case 5:

isFull();

break;

case 6:

display();

break;

case 7:

printf("\n----Exit from program successfully----");

printf("\n--------------Thank you--------------");

exit(0);

}

printf("\n1.Enque\t2.Deque\t3.Peek\t4.isEmpty\t5.isFull\t6.Display\t7.Exit");

printf("\nEnter your choice : ");

scanf("%d",&c);

}while(c);

}

void enque()

{

struct queue *newnode,*temp;

if(top<size-1)

{

newnode=(struct queue *)malloc(sizeof(struct queue));

printf("\nEnter data : ");

scanf("%d",&newnode->data);

newnode->next=0;

top++;

if(head==0)

{

head=temp=newnode;

}

else

{

temp=head;

while(temp->next!=0)

{

temp=temp->next;

}

temp->next=newnode;

}

}

else

{

printf("\nQueue is full");

}

}

void display()

{

struct queue *temp;

temp=head;

while(temp!=0)

{

printf("--%d",temp->data);

temp=temp->next;

}

}

void deque()

{

struct queue *temp,*prevnode;

printf("\n\n----Deletion From End----");

temp=head;

top--;

head=head->next;

free(temp);

printf("\nTop : %d",top);

}

void peek()

{

struct queue *temp;

temp=head;

while(temp->next!=0)

{

temp=temp->next;

}

printf("\nTop : %d",top);

printf("\nPeek : %d",temp->data);

}

void isEmpty()

{

if(top==-1)

{

printf("\nQueue is empty");

}

else

{

printf("\nQueue is not empty");

}

}

void isFull()

{

if(top==size-1)

{

printf("\nQueue is full");

}

else

{

printf("\nQueue is not full");

}

}