pinsert->prior=p;
pinsert->next=p->next;
p->next->prior=pinsert;
p->next=pinsert;  

 p->prior->next=p->next;
  p->next->prior=p->prior;
  free(p);

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define OK 1
#define ERROR 0
#define TRUE 1
#define FALSE 0
typedef int status;
typedef int elemtype;
typedef struct node{
  elemtype data;
  struct node * next;
  struct node * prior;
}node;
typedef struct node* dlinklist;

status visit(elemtype c){
  printf("%d ",c);
}

/*雙向鏈表初始化*/
status initdlinklist(dlinklist * head,dlinklist * tail){
  (*head)=(dlinklist)malloc(sizeof(node));
  (*tail)=(dlinklist)malloc(sizeof(node));
  if(!(*head)||!(*tail))
    return ERROR;
  /*這一步很關(guān)鍵*/ 
  (*head)->prior=NULL;
  (*tail)->next=NULL;
  /*鏈表為空時(shí)讓頭指向尾*/
  (*head)->next=(*tail);
  (*tail)->prior=(*head);
}

/*判定是否為空*/
status emptylinklist(dlinklist head,dlinklist tail){
  if(head->next==tail)
    return TRUE;
  else
    return FALSE;
} 

/*尾插法創(chuàng)建鏈表*/ 
status createdlinklisttail(dlinklist head,dlinklist tail,elemtype data){
  dlinklist pmove=tail,pinsert;
  pinsert=(dlinklist)malloc(sizeof(node));
  if(!pinsert)
     return ERROR;
  pinsert->data=data;
  pinsert->next=NULL;
  pinsert->prior=NULL;
  tail->prior->next=pinsert;
  pinsert->prior=tail->prior;
  pinsert->next=tail;
  tail->prior=pinsert;
} 

/*頭插法創(chuàng)建鏈表*/ 
status createdlinklisthead(dlinklist head,dlinklist tail,elemtype data){
  dlinklist pmove=head,qmove=tail,pinsert;
  pinsert=(dlinklist)malloc(sizeof(node));
  if(!pinsert)
    return ERROR;
  else{
    pinsert->data=data;
    pinsert->prior=pmove;
    pinsert->next=pmove->next;
    pmove->next->prior=pinsert;
    pmove->next=pinsert;
  }
}

/*正序打印鏈表*/ 
status traverselist(dlinklist head,dlinklist tail){
  /*dlinklist pmove=head->next;
  while(pmove!=tail){
    printf("%d ",pmove->data);
    pmove=pmove->next;
  }
  printf("\n");
  return OK;*/
  dlinklist pmove=head->next;
  while(pmove!=tail){
    visit(pmove->data);
    pmove=pmove->next;
  }
  printf("\n");
}

/*返回第一個(gè)值為data的元素的位序*/
status locateelem(dlinklist head,dlinklist tail,elemtype data){
  dlinklist pmove=head->next;
  int pos=1;
  while(pmove&&pmove->data!=data){
    pmove=pmove->next;
    pos++;
  }
  return pos;
}

/*返回表長(zhǎng)*/
status listlength(dlinklist head,dlinklist tail){
  dlinklist pmove=head->next;
  int length=0;
  while(pmove!=tail){
    pmove=pmove->next;
    length++;
  }
  return length;
}

/*逆序打印鏈表*/
status inverse(dlinklist head,dlinklist tail){
  dlinklist pmove=tail->prior;
  while(pmove!=head){
    visit(pmove->data);
    pmove=pmove->prior;
  }
  printf("\n");
}

/*刪除鏈表中第pos個(gè)位置的元素，并用data返回*/
status deleteelem(dlinklist head,dlinklist tail,int pos,elemtype *data){
  int i=1;
  dlinklist pmove=head->next;
  while(pmove&&i<pos){
    pmove=pmove->next;
    i++;
  }
  if(!pmove||i>pos){
    printf("輸入數(shù)據(jù)非法\n");
    return ERROR;
  }
  else{
    *data=pmove->data;
    pmove->next->prior=pmove->prior;
    pmove->prior->next=pmove->next;
    free(pmove);
  }
}

/*在鏈表尾插入元素*/
status inserttail(dlinklist head,dlinklist tail,elemtype data){
  dlinklist pinsert;
  pinsert=(dlinklist)malloc(sizeof(node));
  pinsert->data=data;
  pinsert->next=NULL;
  pinsert->prior=NULL;
  tail->prior->next=pinsert;
  pinsert->prior=tail->prior;
  pinsert->next=tail;
  tail->prior=pinsert;
  return OK;
} 
int main(void){
  dlinklist head,tail;
  int i=0;
  elemtype data=0;
  initdlinklist(&head,&tail);
  if(emptylinklist(head,tail))
    printf("鏈表為空\(chéng)n");
  else
    printf("鏈表不為空\(chéng)n");
  printf("頭插法創(chuàng)建鏈表\n"); 
  for(i=0;i<10;i++){
    createdlinklisthead(head,tail,i);
  }
  traverselist(head,tail);

  for(i=0;i<10;i++){
    printf("表中值為%d的元素的位置為",i); 
    printf("%d位\n",locateelem(head,tail,i));
  }
  printf("表長(zhǎng)為%d\n",listlength(head,tail));
  printf("逆序打印鏈表");
  inverse(head,tail);
  for(i=0;i<10;i++){
    deleteelem(head,tail,1,&data);
    printf("被刪除的元素為%d\n",data);
  }
  traverselist(head,tail);
  if(emptylinklist(head,tail))
    printf("鏈表為空\(chéng)n");
  else
    printf("鏈表不為空\(chéng)n");
    printf("尾插法創(chuàng)建鏈表\n");
  for(i=0;i<10;i++){
    //inserttail(head,tail,i);
    createdlinklisttail(head,tail,i);
  }
  traverselist(head,tail);
  printf("逆序打印鏈表");
  inverse(head,tail);
}