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

typedef struct node_t {
	char *name;
	struct node_t *next;
} node_t;

/* The queue is initially empty. */
node_t *head = NULL;
node_t *tail = NULL;

void insert(const char *name);

int main()
{
	char name[256];
	node_t *new;
	node_t *doomed;
	node_t *p;

	for (;;) {
		printf("Type a name to insert, delete to delete, quit to quit: ");
		scanf("%s", name);
		if (strcmp(name, "quit") == 0) {
			break;
		}

		if (strcmp(name, "delete") != 0) {
			/* Insert a new node at the tail of the queue. */
			new = malloc(sizeof(node_t));
			new->name = malloc(strlen(name) + 1);
			strcpy(new->name, name);

			if (tail == NULL) {
				/* Insert first node into empty queue. */
				head = new;
			} else {
				tail->next = new;
			}
			tail = new;
		}

		else {	/* Remove a node from the head of the queue. */
			if (head == NULL) {
				fprintf(stderr, "The queue is already empty.\n");
				continue;
			}
			doomed = head;
			printf("%s\n", doomed->name);
			if (head == tail) {
				/* The queue is now empty. */
				head = tail = NULL;
			} else {
				head = doomed->next;
			}

			free(doomed->name);
			free(doomed);
		}
	}

	if (head == NULL) {
		printf("The queue is empty.\n");
	} else {
		printf("Here are the people who are still on the queue:\n");
		for (p = head;; p = p->next) {
			printf("%s\n", p->name);
			if (p == tail) {
				break;
			}
		}
	}

	return EXIT_SUCCESS;
}