queuq

/* queue */
#include <stdio.h>
#include <stdlib.h>

struct queue
{
    void *data;
    struct queue *next;
};
typedef struct queue QUEUE;

/* очередь пуста ? */
inline is_queue_empty (QUEUE *head) {return head == NULL;}

void   enqueue (QUEUE **head, QUEUE **tail, void *data);
void  *dequeue (QUEUE **head, QUEUE **tail);

int main (void)
{
    QUEUE *qtail = NULL, *qhead = NULL;
    FILE *fin, *fout;
    int curr_value, prev_value, first = 0;

    if ((fin = fopen("input1.txt", "r")) != NULL)
    {
        while (!feof(fin))
        {
            fscanf(fin, "%d", &curr_value);
            if (first)
            {
                prev_value = curr_value;
                enqueue(&qhead, &qtail, (int *)prev_value);
                first = 0;
            }
            else if (curr_value != prev_value)
            {
                prev_value = curr_value;
                enqueue(&qhead, &qtail, (int *)prev_value);
            }
        }
        fclose(fin);

        if ((fout = fopen("output1.txt", "w")) != NULL)
        {
            while (!(is_queue_empty(qhead)))
                fprintf(fout, "%d\n", dequeue(&qhead, &qtail));

            fclose(fout);
        }
        else
            puts("file could not be created!");
    }
    else
        puts("file could not be opened!");


    system("pause");
    return 0;
}


/* поставить в очередь */
void enqueue (QUEUE **head, QUEUE **tail, void *data)
{
    QUEUE *in = (QUEUE *) malloc(sizeof(QUEUE));
    if (in != NULL)
    {
        in->data = data;
        in->next = NULL;

        if (*head == NULL)
            *head = in;
        else
            (*tail)->next = in;

        *tail = in;
    }
}

/* удалить из очереди */
void *dequeue (QUEUE **head, QUEUE **tail)
{
    QUEUE *tmp;
    void *data;

    data = (*head)->data;
    tmp = *head;
    *head = (*head)->next;

    if (*head == NULL)
       *tail = NULL;

    free(tmp);
    return data;
}