int GetMidNode(LinkList *L,int elem){
  LinkList *search,*mid;
  mid = search = L; //指向頭結(jié)點
  while (search->next != NULL){ //當(dāng)存在下個結(jié)點的時候 
    if (search->next->next!=NULL) {//檢查下個的下個節(jié)點是否為空 
      search = search->next->next;
      mid = mid->next;
    } 
    else
      search = search->next;
  }
  elem = mid->data;
  return elem;
}