unit UQueue;

interface
uses
  StdCtrls, SysUtils;
type
  TElement = Integer;

  TLinkNode = ^TNode;
  TNode = record
    P: TElement;
    Next: TLinkNode;
    Prev: TLinkNode;
  end;
  TMyQueue = class
    _out: TLinkNode;
    _in: TLinkNode;
    constructor Create;
    destructor Destroy;
    function QEmpty: Boolean;
    procedure QClear;
    procedure QAdd(PCB: TElement; prior: integer);
    procedure QDel(var PCB: TElement);
    procedure View(M: TMemo);
  end;

var temp: integer;

implementation

constructor TMyQueue.Create;
begin
  _in := nil;
  _out := nil;
  temp := -5;
end;

destructor TMyQueue.Destroy;
begin
  QClear;
end;

procedure TMyQueue.QAdd(PCB: TElement; prior: integer);
var R: TLinkNode;
begin
  New(R);
  R^.P := PCB;
  R^.Next := nil;
  R^.Prev^.Next := R;
  if qEmpty then
    begin
      _in := R;
      _out := R;
    end
  else
    begin
      if prior >= temp then
        begin
          _in^.Next := R;
          _in := R;
          temp := prior;
        end
      else
        begin
          _in := R;
          _in^.Prev := R;
          temp := prior;
        end;
    end;
end;

procedure TMyQueue.QClear;
var R: TElement;
begin
  while not QEmpty do QDel(R);
  _out := nil;
end;

procedure TMyQueue.QDel(var PCB: TElement);
var R: TLinkNode;
begin
  R := _out;
  if not QEmpty then
  begin
    PCB := R^.P;
    _out := _out^.Next;

    Dispose(R);
  end;
  if _out = nil then
    _in := nil;
end;

function TMyQueue.QEmpty: Boolean;
begin
  QEmpty := _out = nil;
end;

procedure TMyQueue.View(M: TMemo);
var Cur: TLinkNode;
begin
  Cur := _out;
  M.Clear;
  while Cur <> nil do
  begin
    M.Lines.Add(IntToStr(Cur.P));
    Cur := Cur.Next;
  end;
end;


end.