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

typedef int item_t;

typedef struct {item_t *base; 
                int    front; 
                int     rear; 
                int     size;} queue_t;

queue_t *create_queue(int size)
{   queue_t *qu;
    qu = (queue_t *) malloc( sizeof(queue_t) );
    qu->base = (item_t *) malloc( size * sizeof(item_t) );
    qu->size = size;
    qu->front = qu->rear = 0;
    return( qu );
}

int queue_empty(queue_t *qu)
{   return( qu->front == qu->rear );
}

int enqueue( item_t x, queue_t *qu)
{   if ( qu->front != ((qu->rear +2)% qu->size) )
    {   qu->base[qu->rear] = x; 
        qu->rear = ((qu->rear+1)%qu->size);  
        return( 0 );
    }
    else
       return( -1 );
}

item_t dequeue(queue_t *qu)
{   int tmp;
    tmp = qu->front;
    qu->front = ((qu->front +1)%qu->size);
    return( qu->base[tmp] );
}

item_t front_element(queue_t *qu)
{   return( qu->base[qu->front] );
}

void remove_queue(queue_t *qu)
{   free( qu->base ); 
    free( qu );
}

int main()
{  queue_t *qu;
   char nextop;
   qu = create_queue(50);
   printf("Made Array-Based Queue of size 50\n");
   while( (nextop = getchar())!= 'q' )
   { if( nextop == 'e' )
     { int insitem;
       scanf(" %d", &insitem);
       enqueue( insitem, qu );
       printf(" enqueued %d. The current front item is %d\n", insitem,
           front_element(qu) );
     }  
     if( nextop == 'd' )
       { int de_item;
       getchar();
       de_item = dequeue(qu);
       printf("  dequeued item %d", de_item);
       if( queue_empty(qu) )
         printf(" the queue is now empty\n");
       else
         printf(" the front element is now %d\n",  front_element(qu) );

     }
     if( nextop == '?' )
     { getchar();
       if( queue_empty(qu) )
         printf("the queue is empty\n");
       else
         printf("the front element is %d\n", front_element(qu) );
     }
     
   }
   remove_queue(qu);
   printf(" removed queue\n");
   return(0);
}