A.Q[4] B.Q[5] C.Q[14] D.Q[15]
A.8 B.16 C.17 D.18
A.sq.rear= (sq.rear+1)mod MAXSIZE; sq.elem[sq.rear]=x; B.sq.elem[sq.rear]=x; sq.rear= (sq.rear+1)mod MAXSIZE; C.sq.front= (sq.front+1)mod MAXSIZE; sq.elem[sq.front]=x; D.sq.elem[sq.front]=x; sq.front= sq.front+1;