c语言问题

c语言问题

/*DList.h*/#ifndef DList_H  #define DList_H  typedef  int Item;  typedef struct Node * PNode;  typedef PNode Position;  /*定义节点类型*/  typedef struct Node  {      Item data;      /*数据域*/      PNode previous; /*指向前驱*/      PNode next;     /*指向后继*/  }Node;  /*定义链表类型*/  typedef struct  {      PNode head;     /*指向头节点*/      PNode tail;     /*指向尾节点*/      int size;  }DList;    /*分配值为i的节点，并返回节点地址*/  Position MakeNode(Item i);    /*释放p所指的节点*/  void FreeNode(PNode p);    /*构造一个空的双向链表*/  DList* InitList();    /*摧毁一个双向链表*/  void DestroyList(DList *plist);    /*将一个链表置为空表，释放原链表节点空间*/  void ClearList(DList *plist);    /*返回头节点地址*/  Position GetHead(DList *plist);    /*返回尾节点地址*/  Position GetTail(DList *plist);    /*返回链表大小*/  int GetSize(DList *plist);    /*返回p的直接后继位置*/  Position GetNext(Position p);    /*返回p的直接前驱位置*/  Position GetPrevious(Position p);    /*将pnode所指节点插入第一个节点之前*/  PNode InsFirst(DList *plist,PNode pnode);    /*将链表第一个节点删除并返回其地址*/  PNode DelFirst(DList *plist);    /*获得节点的数据项*/  Item GetItem(Position p);    /*设置节点的数据项*/  void SetItem(Position p,Item i);    /*删除链表中的尾节点并返回其地址，改变链表的尾指针指向新的尾节点*/  PNode Remove(DList *plist);    /*在链表中p位置之前插入新节点S*/  PNode InsBefore(DList *plist,Position p,PNode s);    /*在链表中p位置之后插入新节点s*/  PNode InsAfter(DList *plist,Position p,PNode s);    /*返回在链表中第i个节点的位置*/  PNode LocatePos(DList *plist,int i);    /*依次对链表中每个元素调用函数visit()*/  void ListTraverse(DList *plist,void (*visit)());  #endif/*DList.c*/#include"DList.h"  #include  #include  /*分配值为i的节点，并返回节点地址*/  Position MakeNode(Item i)  {      PNode p = NULL;       p = (PNode)malloc(sizeof(Node));      if(p!=NULL)      {          p->data = i;          p->previous = NULL;          p->next = NULL;      }         return p;  }  /*释放p所指的节点*/  void FreeNode(PNode p)  {       free(p);  }  /*构造一个空的双向链表*/  DList * InitList()  {      DList *plist = (DList *)malloc(sizeof(DList));      PNode head = MakeNode(0);       if(plist!=NULL)      {          if(head!=NULL)          {              plist->head = head;              plist->tail = head;              plist->size = 0;          }          else              return NULL;      }      return plist;  }    /*摧毁一个双向链表*/  void DestroyList(DList *plist)  {      ClearList(plist);      free(GetHead(plist));      free(plist);  }    /*判断链表是否为空表*/  int IsEmpty(DList *plist)  {      if(GetSize(plist)==0&&GetTail(plist)==GetHead(plist))          return 1;      else          return 0;  }  /*将一个链表置为空表，释放原链表节点空间*/  void ClearList(DList *plist)  {      PNode temp,p;      p = GetTail(plist);      while(!IsEmpty(plist))      {             temp = GetPrevious(p);          FreeNode(p);          p = temp;          plist->tail = temp;          plist->size--;      }  }    /*返回头节点地址*/  Position GetHead(DList *plist)  {      return plist->head;  }    /*返回尾节点地址*/  Position GetTail(DList *plist)  {      return plist->tail;  }    /*返回链表大小*/  int GetSize(DList *plist)  {      return plist->size;  }    /*返回p的直接后继位置*/  Position GetNext(Position p)  {      return p->next;  }    /*返回p的直接前驱位置*/  Position GetPrevious(Position p)  {      return p->previous;  }    /*将pnode所指节点插入第一个节点之前*/  PNode InsFirst(DList *plist,PNode pnode)  {      Position head = GetHead(plist);        if(IsEmpty(plist))          plist->tail = pnode;      plist->size++;        pnode->next = head->next;      pnode->previous = head;        if(head->next!=NULL)          head->next->previous = pnode;      head->next = pnode;            return pnode;   }    /*将链表第一个节点删除,返回该节点的地址*/  PNode DelFirst(DList *plist)  {      Position head = GetHead(plist);      Position p=head->next;      if(p!=NULL)      {          if(p==GetTail(plist))              plist->tail = p->previous;          head->next = p->next;          head->next->previous = head;          plist->size--;                }         return p;  }    /*获得节点的数据项*/  Item GetItem(Position p)  {      return p->data;  }    /*设置节点的数据项*/  void SetItem(Position p,Item i)  {      p->data = i;  }    /*删除链表中的尾节点并返回地址，改变链表的尾指针指向新的尾节点*/  PNode Remove(DList *plist)  {      Position p=NULL;      if(IsEmpty(plist))          return NULL;      else      {          p = GetTail(plist);          p->previous->next = p->next;          plist->tail = p->previous;          plist->size--;          return p;      }  }  /*在链表中p位置之前插入新节点s*/  PNode InsBefore(DList *plist,Position p,PNode s)  {      s->previous = p->previous;      s->next = p;      p->previous->next = s;          p->previous = s;        plist->size++;      return s;  }  /*在链表中p位置之后插入新节点s*/  PNode InsAfter(DList *plist,Position p,PNode s)  {      s->next = p->next;      s->previous = p;            if(p->next != NULL)          p->next->previous = s;      p->next = s;            if(p = GetTail(plist))          plist->tail = s;            plist->size++;      return s;  }    /*返回在链表中第i个节点的位置*/  PNode LocatePos(DList *plist,int i)  {      int cnt = 0;      Position p = GetHead(plist);      if(i>GetSize(plist)||i<1)          return NULL;        while(++cnt<=i)      {          p=p->next;      }        return p;  }    /*依次对链表中每个元素调用函数visit()*/  void ListTraverse(DList *plist,void (*visit)())  {      Position p = GetHead(plist);      if(IsEmpty(plist))          exit(0);      else      {                    while(p->next!=NULL)          {              p = p->next;              visit(p->data);                    }             }  }