创建头节点：
node *head,*r;
head=neew node;
head->mext=NULL;
r=head;
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
创建新节点：
node *p;
p=new node;
p->data=3;
p->next=NULL;
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
删除节点P后的节点：
p->next=p->next->nextl
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
在节点A后加入新节点B：
b->next=a->next;
a->next=b;
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
双链表的建立：
node *p;
p=new node;
p->data=3;
p->pre=r;
p->next=NULL;
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
创建双链表新节点：
p->pre=r;
r->next=p;
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
双向链表删除P后的节点：
p->pre->next=p->next;
p->next->pre=p->pre;
