QueueLink

program QueueLinkGood;

uses
crt;

type
  TpQueueElement = ^TQueueElement;
  TQueueElement = record
    info : integer;
    next : TpQueueElement;
  end;

var
  pQueueFirst, pQueueLast : TpQueueElement;
  pTemp : ^TQueueElement;
  answer : char;
  element : integer;

procedure push(pushMethodElement : integer);
var
  pTemp : TpQueueElement;
begin
  new(pTemp);
  pTemp^.info := pushMethodElement;
  pTemp^.next := pQueueLast;
  if (pTemp^.next = nil) then
  begin
  pQueueFirst := pTemp;
  end;
  pQueueLast := pTemp;
end;

procedure pop();
var
  pTemp, pTemp2 : TpQueueElement;
begin
  pTemp := pQueueFirst;
  if (pQueueLast <> pQueueFirst) then pTemp2 := pQueueLast^.next else pTemp2 := pQueueLast;
  while true do
  begin
    if ((pTemp = pTemp2^.next) or (pTemp2^.next = nil)) then break;
    pTemp2 := pTemp2^.next;
  end;
  if (pTemp = pTemp2) then
  begin
    pTemp2 := pQueueLast;
  end;
  if (pQueueFirst = pQueueLast) then
  begin
    pQueueFirst := nil;
    pQueueLast := nil;
  end else
  begin
    pQueueFirst := pTemp2;
    pTemp2^.next := nil;
    dispose(pTemp);
  end;
end;

procedure output();
var
  pTemp : TpQueueElement;
begin
  pTemp := pQueueLast;
  while (pTemp <> nil) do
  begin
    write(pTemp^.info, ' ');
    pTemp := pTemp^.next;
  end;
end;

begin
  pQueueFirst := nil;
  pQueueLast := nil;

  repeat
    writeln('1. Add element');
    writeln('2. Remove element');
    writeln('3. Output');
    textColor(4);
    writeln('4. Dispose');
    textColor(7);
    readln(answer);
    case answer of
    '1':
      begin
        write('Enter the new element to add: ');
        readln(element);
        push(element);
      end;
    '2':
      begin
        pop();
        writeln;
      end;
    '3':
      begin
        output();
        writeln;
      end;
    '4':
      begin
        dispose(pQueueLast);
        dispose(pQueueFirst);
      end;
    end;

  until (answer = 'n');

end.