it._p = it._p->_prev ; ++_size ;
return it ; }
void insert(Iterator& it,int n,const T& x)
{ node* p = it._p , * q = p->_prev ;
for(int i=0; i<n; i++)
p = p->_prev = new node(x,q,p) ;
it._p = it._p->_prev = q->_next = p ;
_size += n ;
}
void erase(Iterator& it)
{ if(_size==0) return ;
node* p = it._p ; //temp *p
p->_prev->_next = p->_next ;
p->_next->_prev = p->_prev ;
it._p = p->_next ;
delete p ;
--_size ;
}
};
template<class T>
List<T>::List() : _size(0)
{ _ = new node() ; }
template<class T>
List<T>::~List()
{ node* p = _->_next ;
while(p!= _ )
{ node* pp = p->_next ;
delete p ;
p = pp ;
}
delete _ ;
}
template<class T>
int List<T>::size() const
{ return _size ; }
template<class T>
int List<T>::empty() const
{ return (_size==0 ) ; }
template<class T>
T& List<T>::front() const
{ return _->_next->_data ; }
template<class T>
T& List<T>::back() const
{ return _->_prev->_data ; }
template<class T>
void List<T>::push_front(const T& x)
{ _->_next = _->_next->_prev = new node( x , _ , _->_next ) ;
++_size ;
}
template<class T>
void List<T>::push_back(const T& x)
{ _->_prev = _->_prev->_next = new node( x , _->_prev , _ ) ;
++_size ;
}
template<class T>
void List<T>::printList()
{ node* p = _->_next ;
while(p!= _ )
{ cout<<p->_data<<" " ;
p = p->_next ;
}
}
template<class T>
void List<T>::clear()
{ node* p = _ , * q=p->_next ;
while(q!=p)
{ p->_next = q->_next ;
q->_next->_prev = p ;
delete q ;
q = p->_next ;
}
_size = 0 ;
}
template<class T>
void List<T>::showList()
{ Iterator ip(_),it(_->_next) ;
while(it!=ip)
{ cout<<*(it)<<" ";
++it;
}
}
void main()
{
List<int> lst ;
clrscr() ;
lst.push_front(3) ; lst.push_front(9) ;
lst.push_back(8) ; lst.push_back(4) ;
lst.printList() ;
cout<<endl<<lst.front()<<" "<<lst.back() ;
getch();
cout<<endl;
lst.erase(lst.begin()) ;
cout<<*(lst.begin())<<" "<<*(lst.end()) ;
getch();
cout<<endl;
lst.showList() ;
getch() ;
}
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