void reverselist(void)

{

if(head==0)

return;

if(head->next==0)

return;

if(head->next==tail)

{

head->next = 0;

tail->next = head;

}

else

{

node* pre = head;

node* cur = head->next;

node* curnext = cur->next;

head->next = 0;

cur-> next = head;

for(; curnext!=0; )

{

cur->next = pre;

pre = cur;

cur = curnext;

curnext = curnext->next;

}

curnext->next = cur;

}

}