// Queue implementation in C

#include <stdio.h>
#include <stdlib.h>
#define SIZE 5

void enqueue();
void dequeue();
void display();

int items[SIZE], front = -1, rear = -1;

int main() {
  //deQueue is not possible on empty queue
  int x;
  
  printf("1 for enqueue\n");
  printf("2 for dequeue\n");
  printf("3 for display\n");
  printf("0 for exit\n");
  while(1)
  {
      printf("enter choise:");
      scanf("%d",&x);
      
      switch(x)
      {
        case 1:
            enqueue();
            break;
        case 2:
            dequeue();
            break;
        case 3:
            display();
            break;
        case 0:
            exit(1);
            printf("EXIT");
        default:
            printf("plz enter valid number\n");
      }
  }

  return 0;
}

void enqueue(){
    int value;
    
    printf("enter value to enqueue:");
    scanf("%d",&value);
    
  if (rear == SIZE - 1)
    printf("\nQueue is Full!!");
  else {
    if (front == -1)
      front = 0;
    rear++;
    items[rear] = value;
    printf("\nInserted -> %d\n", value);
  }
}

void dequeue(){
  if (front == -1)
    printf("\nQueue is Empty!!");
  else {
    printf("\nDeleted : %d\n", items[front]);
    front++;
    if (front > rear)
      front = rear = -1;
  }
}

// Function to print the queue
void display(){
  if (rear == -1)
    printf("\nQueue is Empty!!!");
  else {
    int i;
    printf("\nQueue elements are:\n");
    for (i = front; i <= rear; i++)
      printf("%d  ", items[i]);
  }
  printf("\n");
}