列表中不需要的额外元素和列表的反向顺序

Question

大家好，我有这个代码。我必须从记录文件中创建一个列表，其中我有数据列( position, time, flags)。一切都很顺利但是当我在std输出上打印时，列表中有1个额外的零元素，列表又回到了前面。有人可以向我解释原因吗？ 非常感谢大家！

这是我从输出中得到的一个例子：

::(0.0,0.000000000000000,OK)

::(14000.0,314.000023350630840,OK)

::(21000.0,314.000035023289740,OK)

::(736000.0,314.001227515303469,OK)

::(647000.0,314.001079063932764,NOISE)

::(70000.0,314.000116745763364,OK)

::(487000.0,314.000812207375702,OK)

::(81000.0,314.000135099892645,OK)

::(917000.0,314.001529387085043,NOISE)

::(871000.0,314.001452666758723,OK)

::(380000.0,314.000633767941338,OK)

::(578000.0,314.000964003751733,OK)

::(289000.0,314.000481997603799,OK)

::(597000.0,314.000995684957161,OK)

::(480000.0,314.000800553021577,OK)

::(264000.0,314.000440315509820,OK)

::(408000.0,314.000680456580596,OK)

::(603000.0,314.001005693768377,OK)

::(757000.0,314.001262536680713,OK)

::(369000.0,314.000615422503131,OK)

::(458000.0,314.000763851368049,OK)

以下是代码：

typedef enum { NOTORD=0, TIME=1, POSITION=2  } ord_t;  //list order: 0 not ordered, 1 ordered by time, 2 ordered by position
typedef enum { OK=0, NOISE=2  } flag_t;    //good/bad record

typedef struct elem {
  /** position record*/
  double position;
  /** time record */
  double time;
  /** flag noise/good */
  flag_t flag;
  /** pointer to next element */
  struct elem * next;
} elem_t;

typedef struct {
  /** pointer to headof list */
  elem_t * head;
  /** nnumber of element in list */
  int nelem; 
  /** indicate the type of order of the list  */
  ord_t ord; 
} lista_t;

lista_t * new_lista ( void ) {       //list creation

  lista_t * l ;

  if ( (  l = malloc (sizeof ( lista_t ) ) ) == NULL ) {
    return NULL;
  }

  l->head = NULL ;
  l->nelem = 0 ;
  l->ord = NOTORD;
  return l;  
} 

elem_t* leggi_registrazione (FILE* fd) {     //read records from file
elem_t * puntolista;

if (!feof(fd))
    {
        puntolista=malloc(sizeof(elem_t));
        fscanf(fd, "%lf", &(puntolista->position));
        fscanf(fd, "%lf", &(puntolista->time));
        fscanf(fd, "%d", (int *)&(puntolista->flag));
        puntolista->next= NULL;    
        return puntolista;}

else {return NULL;}
} 

static void stampa_lista_r ( FILE * f, elem_t * h ) {    //list print funct to use in stampa_lista
  if ( h == NULL ) {
    return ;
  }
  if ( h->flag == OK ) fprintf(f,"::(%.1f,%.15f,OK)\n",h->position, h-    >time);
  if ( h->flag == NOISE ) fprintf(f,"::(%.1f,%.15f,NOISE)\n",h->position, h->time);
  stampa_lista_r(f, h->next);
}

void stampa_lista ( FILE * f, lista_t * l ) {     //list print function

  if ( l == NULL ) return ;

  if ( l-> head == NULL ) {
    fprintf(stdout,"Lista vuota.\n");
    return ;
  }   
  stampa_lista_r (f,l->head);
  putchar('\n');
  return ;  
}

int inserisci ( lista_t * l , elem_t* pelem) {     //element insert in list
elem_t *prec;
    elem_t *corr;
    elem_t *aux;
    int trovato = 0;
      if (l->ord==NOTORD)                           //not ordered list
        {   
                                                //insert at the beginning
            aux = malloc(sizeof(elem_t));
            aux->position = pelem->position;
            aux->time = pelem->time;
            aux->flag = pelem->flag;
            aux->next = l->head;
            l->head = aux;
            return 0;
        }
    if (l->ord==TIME)                        //time ordered list
    {   

        prec=malloc(sizeof(elem_t));
        corr=malloc(sizeof(elem_t));
        prec = l->head;
        corr = prec -> next;
        trovato = 0;
            while (corr !=NULL && !trovato)
            {
             if ((corr -> time) >= (pelem->time))
             trovato = 1;
             else
             {prec = prec -> next;
             corr = corr -> next;}
            }
        aux = malloc(sizeof(elem_t));         //alloc and insert in list
        aux->position = (pelem->position);
        aux->time = (pelem->time);
        aux->flag = (pelem->flag);
        prec -> next = aux;
        aux -> next = corr;
        return 0;
    }
    if (l->ord==POSITION)                   //position ordered list
    {   
        prec=malloc(sizeof(elem_t));
        corr=malloc(sizeof(elem_t));
        prec = l->head;
        corr = prec -> next;
        trovato = 0;
            while (corr !=NULL && !trovato)
            {
             if ((corr -> position) >= (pelem->position))
             trovato = 1;
             else
             {prec = prec -> next;
             corr = corr -> next;}
            }
        aux = malloc(sizeof(elem_t));         //alloc and insert in list
        aux->position = (pelem->position);
        aux->time = (pelem->time);
        aux->flag = (pelem->flag);
        prec -> next = aux;
        aux -> next = corr;
        return 0;
    }
    else return -1;
}

int main (void) 
{
  FILE* f;            // pointer to record file
  lista_t * ll;
  elem_t* pelem;
  int err;
   char buf[N+2];

 f = fopen (FILE1,"r");
  if ( f == NULL ) {
    perror("fopen");
    exit(EXIT_FAILURE);
  }
  /* delete first line in external file(it's a comment) */
  if ( fgets(buf,N+2,f) == NULL ) exit(EXIT_FAILURE);
  if (buf[0] != '#') exit(EXIT_FAILURE);
 /* read records and insert in new list */
  ll = new_lista();

  while ( ( pelem = leggi_registrazione(f) ) != NULL ) {
    /* insert in list in reading order */
    err = inserisci (ll,pelem);
    if ( err == -1 ) return EXIT_FAILURE;
 }   
 /* results print */
 stampa_lista(stdout,ll) ;


return 0;}