program for dequeue

#include<stdio.h>

#include<conio.h>

#define MAX 50

struct queue

{

      int a[MAX];

      int rear,front;

}

st;

void enqueuefront(int x);

void enqueuerear(int x);

void dequeuefront();

void dequeuerear();

void display();

void main()

{

      int op,x;

      st.rear=st.front=-1;

      do

      {

            printf("\n1.Insertion from rear\n2.Insertion from front\n3.Deletion from rear\n4.Deletion from front\n5.Print\n6.Exit");

            printf("\nEnter choice");

            scanf("^D",&op);

            switch(op)

            {

                  case 1:if((st.rear+1)%MAX==st.front)

                  printf("\nFull queue");

                  else

                  enqueuerear(x);

                  break;

                  case 2:if((st.rear+1)%MAX==st.front)

                  printf("\nFull queue");

                  else

                  enqueuefront(x);

                  break;

                  case 3:if(st.rear==-1)

                  printf("\nEmpty queue");

                  else

                  {

                        dequeuerear();

                  }

                  break;

                  case 4:if(st.front==-1)

                  printf("\nEmpty queue");

                  else

                  {

                        dequeuefront();

                  }

                  break;

                  case 5:display();

                  break;

            }

      }while(op!=6);

      getch();

}

void enqueuerear(int x)

{

      printf("\nEnter data:");

      scanf("%d",&x);

      if(st.rear==-1&&st.front==-1)

      {

            st.rear=0;st.front=0;

            st.a[0]=x;

      }

      else

      {

            st.rear=(st.rear+1)%MAX;

            st.a[st.rear]=x;

      }

}

void enqueuefront(int x)

{

      printf("\nEnter data:");

      scanf("%d",&x);

      if(st.rear==-1&&st.front==-1)

      {

            st.rear=0;st.front=0;

            st.a[0]=x;

      }

      else

      {

            st.front=(st.front-1+MAX)%MAX;

            st.a[st.front]=x;

      }

}

void dequeuerear()

{

      int y;

      if(st.rear==st.front)

      {

            y=st.a[st.rear];

            st.front=-1;

            st.rear=-1;

      }

      else

      {

            y=st.a[st.rear];

            st.rear=(st.rear-1+MAX)%MAX;

      }

            printf("\nDeleted element=%d",y);

      }

void dequeuefront()

{

      int y;

      if(st.rear==st.front)

      {

            y=st.a[st.front];

            st.front=-1;

            st.rear=-1;

      }

      else

      {

            y=st.a[st.front];

            st.front=(st.front+1)%MAX;

      }

            printf("\nDeleted element=%d",y);

      }

void display()

{

      int i;

      if(st.rear==-1&&st.front==-1)

      printf("\nEmpty queue");

      else

      {

            printf("\nQueue is:");

            i=st.front;

            while(i!=st.rear)

            {

                  printf("<%d>",st.a[i]);

                  i=(i+1)%MAX;

            }

            printf("<%d>",st.a[st.rear]);

      }

}