double ended queue (deque)-Data Structure developerIndian.com

Updated:13/08/2023 by Computer Hope

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In this tutorial, you will learn what a double ended queue (deque) is. Also, you will find working examples of different operations on a deque in C, C++, Java and Python

#include<stdio.h>
#include<conio.h>
#define MAX 10
int queue[MAX];
int f=-1,r=-1;
void insertrear(int no)
  {
  if((f==0&&r==MAX-1)||(r+1==f))
     {
     printf("\nQueue is Full");
     return;  }
   else
     {  if(r==-1)
	   f=r=0;
	else if(r==MAX-1)
	   r=0;
	else
	  r++;
	queue[r]=no;
      }
  }
void insertfront(int no)
  {
  if((f==0&&r==MAX-1)||(r+1==f))
     {
     printf("\nQueue is Full");
     return;  }
   else
     {  if(r==-1)
	   f=r=0;
	else if(f==0)
	   r=MAX-1;
	else
	  f--;
	queue[f]=no;
      }
  }
int deletefront( )
 {
 int val;
   if(f==-1)
     { printf("\nQueue is Empty");
       return -999;
      }
   else
    { val=queue[f];
       if(f==r)
	  f=r=-1;
       else if(f==MAX-1)
	  f=0;
       else
	  f++;
     }
  return val;
 }
int deleterear()
  {  int val;
    if(r==-1)
     { printf("\nQueue is Empty");
       return -999; }
  else
    { val=queue[r];
      if(f==r)
	 f=r=-1;
      else if(r==0)
        r=MAX-1;
      else
        r--;  }
  return val;
}
void  show( )
   {
     int i=f;
    if(f==-1)
     {  printf("\nQueue is Empty");
	return; }
   while(i!=MAX)
     {  printf("%d  ",queue[i]);
	if(i==r)
	  break;
	else if(i==MAX-1)
	  i=0;
	else
	  i++;
      }
    }
void main()
{
  int  ch,n;
  do
  {
    clrscr();
    printf("\n1. Insert in Front");
    printf("\n2. Insert in Rear");
    printf("\n3. Delete from Front");
    printf("\n4. Delete from Rear");
    printf("\n5. Show");
    printf("\n0. Exit");
    printf("\n\nEnter Your Choice");
    scanf("%d",&ch);
    switch(ch)
    {
      case 1:printf("\nEnter Number ");
	     scanf("%d",&n);
	     insertfront(n);
	     break;
      case 2:printf("\nEnter Number ");
	     scanf("%d",&n);
	     insertrear(n);
	     break;
      case 3:n=deletefront();
	     if(n!=-999)
	       printf("\n%d deleted",n);
	     break;
      case 4:n=deleterear();
	     if(n!=-999)
	       printf("\n%d deleted",n);
	     break;
      case 5:show();
	     break;
      case 0:break;
      default:printf("\nWrong Choice...Try Again");
    }
  }while(ch!=0);
}

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