void reverse(Link *& head){
if(head==NULL) return;
Link *pre,*cur,*next;
pre=head;
cur=head->next;
while(cur){
next=cur->next;
cur->next=pre;
pre=cur;
cur=next;
}
head->next=NULL;
head=pre;
}
void reverse(Link *& head){
if(head==NULL) return;
Link *pre,*cur,*next;
pre=head;
cur=head->next;
while(cur){
next=cur->next;
cur->next=pre;
pre=cur;
cur=next;
}
head->next=NULL;
head=pre;
}