Dequeue | Data Structure | C Program

Dequeue:

Code:

#include<stdio.h>
#define MAX 5
int rear=-1;
int front=-1;
int cq[MAX];
void inf();
void inr();
void def();
void der();
void di();
void main()
{
 int ch;
 while(1)
 {
  printf("\nChoose any option\n1.Insert from front \t2.Insert from rear\n3.Delete from front\t4.Delete from rear\n5.Display\n");
  scanf("%d",&ch);
  switch(ch)
  {
   case 1:
    inf();
    break;
   case 2:
    inr();
    break;
   case 3:
    def();
    break;
   case 4:
    der();
    break;
   case 5:
    di();
    break;
  }
 }
}
void inf()
{
 int item;
 if((front==0 && rear==MAX-1) || front==rear+1)
  printf("Queue is full\n");
 else
 {
  printf("Enter a value\n");
  scanf("%d",&item);
  if(front==-1)
  {
   front=0;
   rear=0; 
  }
  else if(front==0)
  {
   front=MAX-1;
  }
  else
   front=front-1;
  cq[front]=item;
 }

}
void der()
{
 int item;
 if(rear==-1)
  printf("Queue Underflow!!\n");
 else
 {
  item=cq[rear];
  if(front==rear)
  {
   front=-1;
   rear=-1;
  }
  else if(rear==0)
   rear==MAX-1;
  else
   rear=rear-1;
  printf("%d is deleted\n",item);
 }
}
void inr()
{
 int item;
 if((front==0 && rear==MAX-1) || front==rear+1)
 {
  printf("Queue is full!!\n");
 }
 else
 {
  printf("Enter a value\n");
  scanf("%d",&item);
  if(front==-1)
   front=0,rear=0;
  else if(rear==MAX-1)
   rear=0;
  else
   rear=rear+1;
  cq[rear]=item;
 }
}
void def()
{
 int item;
 if(front==-1)
  printf("Queue underflow!!\n");
 else
 {
  item=cq[front];
  printf("You deleted %d\n",item);
  if(rear==front)
  { 
   rear=-1;
   front=-1;
  } 
  else if(front==MAX-1)
  {
   front=0;
  }
  else
  {
   front=front+1;
  } 
 }
}
void di()
{
 int i;
 if(front==-1)
 {
  printf("Queue is empty!!\n");
  for(i=0;i<MAX;i++)
   printf("_\t");
 }
 else
 {
  if(front<=rear)
  {
   for(i=0;i<front;i++)
             printf("_\t");
         for(i=front;i<=rear;i++)
             printf("%d\t",cq[i]);
         for(i=rear+1;i<MAX;i++)
             printf("_\t");
  }
  else
  {
   for(i=0;i<=rear;i++)
    printf("%d\t",cq[i]);
   for(i=rear+1;i<front;i++)
    printf("_\t");
   for(i=front;i<MAX;i++)
    printf("%d\t",cq[i]);
  }
 }
}

Output:

------------------------------------------------------------
Circular Queue : >>>  CQueue   <<<