P126 练习4.1 E2
(a)Node *p0=new Node('0');
Node *p1=p0 -> next=new Node('1');
p1->next=NULL;
(b)Node *p0=new Node('0');
Node *p1=new Node('1',p0);
Node *p2=p1;
(c)Node *p0=new Node('0');
Node *p1=p0 ->next=new Node('1');
Node *p2=p1 ->next=new Node('2',p1);