typedef struct node {       struct node *prior;       struct node *next;        int num; }NODE; /*******双向链表的初始化********/ NODE *Init_link(void) {      int i;      NODE *phead,*pb,*pi;      phead = (NODE *)malloc(sizeof(NODE));      printf("please input num:\n");      scanf("%d",&(phead->num));      phead->prior = NULL;      phead->next = NULL;      pb = phead;      for(i=0; i<3; i++)      {           pi = (NODE *)malloc(sizeof(NODE));           printf("please input num:\n");               scanf("%d",&(pi->num));           pi->next = NULL;           pb->next = pi;           pi->prior = pb;           pb = pi;      }      return phead; } /******链表的输出******/ void print_link(NODE *phead) {  while(phead != NULL)  {   printf(" %d,",phead->num);   phead = phead->next;  }  printf("\n"); } /******链表的逆序******/ NODE *reverse_link(NODE *phead) {  NODE *pb,*pf,*temp;  pb = phead;  pf = pb->next;  while(pf != NULL)  {   temp = pf->next;   pf->next = pb;   pb->prior = pf;   pb = pf;   pf = temp;  } // phead->prior = pf->prior;  phead->next = NULL;  phead = pb;  return phead; } /*****链表的排序*****/ NODE *Order_link(NODE *phead) {      NODE *pb,*pf,*ptr,temp;      pb = phead;      while(pb->next != NULL)      {           pf = pb->next;           while(pf != NULL)           {                if(pb->num > pf->num)                {                      temp = *pb;                     *pb = *pf;                     *pf = temp;                      ptr = pb->next;                      pb->next = pf->next;                      pf->next = ptr;                      ptr = pb->prior;                      pb->prior = pf->prior;                      pf->prior = ptr;               }              pf = pf->next;         }         pb = pb->next;     }     return phead; } /******链表的有序插入*****/ NODE *insert_link(NODE *phead,NODE *pi) {  NODE *pb,*pf;  pb = phead;  if(pi == NULL)   return phead;  if(phead == NULL)  {   phead = pi;   pi->prior = NULL;   pi->next =NULL;  }  else  {   while( (pi->num > pb->num)&&(pb->next!=NULL))   {    pf = pb;    pb = pb->next;   }   if(pi->num <= pb->num)   {    if(pb == phead)    {     pi->next = phead;     pi->prior = NULL;     phead->prior = pi;     phead = pi;    }    else    {     pi->next = pb;     pb->prior = pi;     pi->prior = pf;     pf->next = pi;    }   }   else   {    pi->next = NULL;    pi->prior = pb;    pb->next = pi;   }  }  return phead; } /******链表的删除*****/ NODE *delete_link(NODE *phead, NODE *pi) {  NODE *pb,*pf;  pb = phead;  while(pb != NULL)  {   if(pb == pi)   {    if(pb == phead)     phead = phead->next;    else if(pb->next == NULL)     pf->next = NULL;    else    {     pf->next = pb->next;     //pb->next->prior = pf;    }   }   pf = pb;   pb = pb->next;  }  return phead; } /*******链表的释放******/ void free_link(NODE *phead) {  NODE *pb;  while(phead != NULL)  {   pb = phead->next;   free(phead);   phead = pb;  }  printf("released link success!\n"); } /*******测试程序******/ int main(void) {  NODE *phead,*pi;  phead = Init_link();  printf("init link:\n");  print_link(phead);  pi = (NODE *)malloc(sizeof(NODE));  printf("plaese input insert num:");  scanf("%d",&(pi->num));  phead = insert_link(phead,pi);  printf("after insert link：\n");  print_link(phead);  phead = Order_link(phead);  printf("after sort link:\n");  print_link(phead);  printf("after reverse link:\n");  phead = reverse_link(phead);  print_link(phead);  phead = delete_link(phead, pi);  printf("after delete link:\n");  print_link(phead);  free_link(phead);  return 0; }