#include <stdio.h>
#include <stdlib.h>

void enqueue(int);
void dequeue(void);
void display_queue(void);
void queue_size(void);
void rear_and_front(void);

struct node{
  int data;
  struct node *next;
}*start=NULL;

struct node *front, *rear;

int main(){
  int choice, ele;
  while(1){
    printf("Enter 1 to Enqueue\n");
    printf("Enter 2 to Dequeue\n");
    printf("Enter 3 to display Queue\n");
    printf("Enter 4 to show Queue size\n");
    printf("Enter 5 to display Front and Rear elements\n");
    scanf("%d",&choice);
    switch(choice){
      case 1: printf("Enter the element\n");
              scanf("%d",&ele);
              enqueue(ele);
              break;
      case 2: dequeue();
              break;
      case 3: display_queue();
              break;
      case 4: queue_size();
              break;
      case 5: rear_and_front();
              break;
      default: printf("Invalid choice\n");
    }
  }
  return 0;
}

void enqueue(int ele){
  struct node *temp, *p;
  temp = (struct node*)malloc(sizeof(struct node));
  if(start == NULL){
    temp -> data = ele;
    temp -> next = NULL;
    start = temp;
    rear = front = temp;
    printf("Added %d to Queue!!\n",start->data);
  }
  else{
    p = start;
    while(p->next != NULL){
      p = p->next;
    }
    temp = (struct node*)malloc(sizeof(struct node));
    temp -> data = ele;
    temp -> next = NULL;
    p -> next = temp;
    rear = temp;
    printf("Added %d to Queue!!\n",temp->data);
  }
}

void dequeue(){
  struct node *front;
   if (start == NULL){
     printf("No element to remove\n");
   }
   else{
     start = start -> next;
     front = start;
     printf("Item successfully removed!!\n");
   }
}

void display_queue(){
  struct node *p;
   p = start;
   if (p == NULL){
     printf("List is empty\n");
   }
   else{
     while(p != NULL){
     printf("%d\t",p->data);
     p = p->next;
   }
   printf("\n");
   }
}

void queue_size(){
   int count = 1;
   if (start == NULL){
     printf("Queue is empty!!\n");
   }
   else{
   while(start -> next != NULL){
      count++;
      start = start->next;
   }
   printf("Size of queue : %d\n", count);
   }
}

void rear_and_front(){
  if(start == NULL){
    printf("Queue is empty!\n");
  }
  else{
    printf("FRONT -> %d\t",front -> data);
    printf("REAR -> %d\n",rear -> data );
  }
}