#include<iostream.h>
#include<stdlib.h>
#include<iomanip.h>

void Exception(int Condition,   char *ErrorMsg){
	if(Condition){cerr << ErrorMsg << endl; abort();}
}

template <class T> class Chain;

template <class T>
class ChainNode{
   friend class Chain<T>;
   private:
//	public:
      T data;
      ChainNode<T> *link;
};

template<class T>
class Chain {
   public:
      Chain();
      ~Chain();
	  void Clear();      //清空链表
      bool IsEmpty() const {return first->link == 0;}
      int Length() const; 
	  T Get(int k) const;  //返回第i个结点的值
	  int Find(const T e) const; //返回值等于e的结点的序号，无则返回0
      //int Search(const T& x) const; 
      bool Delete(int k, T &x); 
      bool Insert(int k, const T x);
      void Output(ostream& out) const;
   private:
      ChainNode<T> *first;  // pointer to first node
};

template<class T>
Chain<T>::Chain(){    //构造函数
	first = new ChainNode<T>;  //申请连续空间，返回空间首地址
	Exception(!first, "there is no space in memory"); //若申请空间失败，则程序中断
	first->link = 0;
}

template<class T>
Chain<T>::~Chain()
{// Chain destructor. Delete all nodes in chain.
   ChainNode<T> *next;  // next node
   while (first) {
      next = first->link;
      delete first;
      first = next;
      }
}

template<class T>
void Chain<T>::Clear()      //清空链表
{
   ChainNode<T> *next1, *next2;  // next node
   next1 = first->link;
   while (next1) {
      next2 = next1->link;
      delete next1;
      next1 = next2;
      }
   first->link = 0;
}


template<class T>
int Chain<T>::Length() const
{// Return the number of elements in the chain.
   ChainNode<T> *current = first->link;
   int len = 0;
   while (current) {
     len++;
     current = current->link;
     }
   return len;
}

template<class T>
T Chain<T>::Get(int k) const
{// Set x to the k'th element in the chain.
 // Return false if no k'th; return true otherwise.
   Exception(k<1, "Out of bounds access."); //越界、非法
   ChainNode<T> *current = first->link;
   int index = 1;  // index of current
   while (index < k && current) {
      current = current->link;
      index++;
      }
   Exception(!current, "Out of bounds access."); //越界、非法
   return current->data;
}

template<class T>
int Chain<T>::Find(const T x) const
{// Locate x.  Return position of x if found.
 // Return 0 if x not in the chain.
   ChainNode<T> *current = first->link;
   int index = 1;  // index of current
   while (current && current->data != x) {
      current = current->link;
      index++;
      }
   if (current) return index;
   return 0;
}

template<class T>
bool Chain<T>::Delete(int k, T &x)
{// Set x to the k'th element and delete it.
 // Throw OutOfBounds exception if no k'th element.
   Exception((k < 1 || !first->link), "Out of bounds access.");
   
   // move q to k-1'th 
      ChainNode<T> *q = first;
      for (int index = 0; index < k - 1 && q->link; index++)
         q = q->link;
 
     Exception(!(q->link), "Out of bounds access."); // no k'th
	    // p will eventually point to k'th node
      ChainNode<T> *p = q->link; // k'th
      q->link = p->link; // remove from chain

   // save k'th element and free node p
   x = p->data;
   delete p;
   return true;
}

template<class T>
bool Chain<T>::Insert(int k, const T x)
{// Insert x at the k'th element.
 // Throw OutOfBounds exception if no k'th element.
 // Pass NoMem exception if inadequate space.
   Exception((k <= 0), "Out of bounds access.");

   // p will eventually point to k-1'th node
   ChainNode<T> *p = first;
   for (int index = 0; (index < k-1) && p; index++)  // move p to k'th
      p = p->link;
   Exception((!p), "Out of bounds access."); // no k'th

   // insert
   ChainNode<T> *y = new ChainNode<T>;
   y->data = x;
           y->link = p->link;
           p->link = y;
   return true;
}

template<class T>
void Chain<T>::Output(ostream& out) const
{// Insert the chain elements into the stream out.
   ChainNode<T> *current;
   for (current = first->link; current;
                         current = current->link)
      out << current->data << "  ";
}

// overload <<
template <class T>
ostream& operator<<(ostream& out, const Chain<T>& x)
   {x.Output(out); return out;}

void main(void)
{
   try {
      Chain<int> L;
      cout << "Length = " << L.Length() << endl;
      cout << "IsEmpty = " << L.IsEmpty() << endl;
      L.Insert(1,2);L.Insert(1,6);
      cout << "List is " << L << endl;
      cout << "IsEmpty = " << L.IsEmpty() << endl;
      int z;
      cout << "First element is " << L.Get(1) << endl;
      cout << "Length = " << L.Length() << endl;
      L.Delete(1,z);
      cout << "Deleted element is " << z << endl;
      cout << "List is " << L << endl;
      }
   catch (...) {
      cerr << "An exception has occurred" << endl;
      }
}