A.front=front->next B.rear=rear->next C.rear=front->next D.front=rear->next
A.rear%n= = front B.front+l= rear C.rear= = front D.(rear+l)%n= front
A.rear%n= = front B.(front+l)%n= = rear C.rear%n -1= = front D.(rear+l)%n= = front