UNIT QUEUE;

INTERFACE TYPE

QueueElement= integer;

QueuePtr=^QueueNode;

QueueNode=record

Du_lieu:QueueElement;

Next:QueuePtr;

end;

QueueType=record

front,rear:QueuePtr;

end;

Procedure CreateQ(Var Queue:QueueType);

Function EmptyQ(Queue:QueueType):Boolean;

Procedure AddQ(Var Queue:QueueType;Item:QueueElement);

Procedure RemoveQ(Var Queue:QueueType;var Item:QueueElement);

IMPLEMENTATION

Procedure CreateQ(Var Queue:QueueType);

Begin

Queue.front:=Nil;Queue.rear:=NIL;end;

Function EmptyQ(Queue:QueueType):Boolean;

Begin

EmptyQ:=(Queue.front=Nil) and (Queue.rear=Nil) end;

Procedure AddQ(Var Queue:QueueType;Item:QueueElement);

Var Pt:QueuePtr;

Begin

New(Pt);

Pt^.Du_lieu:=Item;

With Queue do

If EmptyQ(Queue) then

Begin front:=Pt;rear:=Pt end

else

Begin Rear^.Next:=Pt;Rear:=Pt end;

end;

Procedure RemoveQ(var Queue:QueueType;Var Item:QueueElement);

Var Pt:QueuePtr;

Begin

If EmptyQ(Queue) Then Writeln('Hang Doi Rong')

else With Queue Do

Begin Item:=Front^.Du_lieu;

Pt:=Front;

If Front<>rear then Front:=Front^.Next

Else Begin Front:=Nil;Rear:=Nil end;

Dispose(Pt);

end;

End;

End.