Моделирование защиты работ студентами

 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
struct node {
    char *p;
    struct node *next;
};
 
struct queue {
    struct node *head, *tail;
};
 
void CreateQueue(struct queue *pq);
void ClearQueue(struct queue *pq);
int PutQueue(struct queue *pq, struct node *pn);
int GetQueue(struct queue *pq, struct node *pn);
 
/* creates a queue, puts there some elements
   reads the queue and prints every element */
int main(void)
{
    struct queue q;
    struct node n = { "one", NULL };
    struct node m = { "two", NULL };
    
    CreateQueue(&q);
    
    PutQueue(&q, &n);
    PutQueue(&q, &m);
    PutQueue(&q, &n);
    PutQueue(&q, &m);
    PutQueue(&q, &n);
    PutQueue(&q, &m);
        
    while (GetQueue(&q, &n) != 0)
        printf("%s" "\n", n.p);
    
    return EXIT_SUCCESS;
}
 
/* CreateQueue:  creates a clear queue pq */
void CreateQueue(struct queue *pq)
{
    pq->head = pq->tail = NULL;
}
 
/* ClearQueue:  clears a queue pq */
void ClearQueue(struct queue *pq)
{
    struct node *tmp;
    
    while ((tmp = pq->head) != NULL) {
        pq->head = tmp->next;
        free(tmp);
    }
    pq->tail = NULL;
}
 
/* PutQueue:  puts to a queue pq a node pn;
              returns 1 or 0 */
int PutQueue(struct queue *pq, struct node *pn)
{
    struct node *tmp;
    
    tmp = (struct node *) malloc(sizeof(struct node));
    
    if (tmp == NULL)
        return 0;
    
    *tmp = *pn;
    tmp->next = NULL;
    
    if (pq->head == NULL)
        pq->head = pq->tail = tmp;
    else {
        pq->tail->next = tmp;
        pq->tail = tmp;
    }
    
    return 1;
}
 
/* GetQueue:  gets from a queue pq a node pn;
              returns 1 or 0 */
int GetQueue(struct queue *pq, struct node *pn)
{
    struct node *tmp;
    
    if (pq->head == NULL) {
        pq->tail = NULL;
        return 0;
    }
    
    tmp = pq->head;
    *pn = *tmp;
    pq->head = tmp->next;    
    free(tmp);
    
    return 1;
}