Удалить из списка все элементы с нечетными номерами

type
 
  TElement = Integer;
  PNode = ^TNode;
  TNode = record
    prev, next: PNode;
    data: TElement;
  end;
 
function NewNode(n: TElement; pFirst: PNode): PNode;
begin
  if pFirst = nil then begin
    New(pFirst);
    pFirst^.Next := nil; pFirst^.Prev := nil;
  end else begin
    New(pFirst^.Prev);
    pFirst^.Prev^.Next := pFirst;
    pFirst^.Prev^.Prev := nil;
    pFirst := pFirst^.Prev;
  end;
  pFirst^.data := n;
  NewNode := pFirst;
end;
 
procedure sPush(var lst: PNode; n: TElement);
begin
  lst := NewNode(n, lst);
end;
 
function sPop(var lst: PNode): TElement;
var
  t: PNode;
begin
  if lst=nil then WRITELN('ERROR');
  with lst^ do 
  begin
    sPop := data;
    t := lst; lst := next; Prev := nil; Dispose(t);
  end;
end;
 
procedure sWrite(lst: PNode);
begin
  while lst <> nil do 
  begin
    Write(' ', lst^.data);
    lst := lst^.next;
  end;
end;
 
procedure sDeleteEven(lst: PNode);
var
  t, t1: PNode;
begin
  while (lst <> nil) and (lst^.next <> nil) do 
  begin
    t := lst^.next;
    t1 := lst;
    lst^.next := lst^.next^.next;
    Dispose(t);
    lst := lst^.next;
    if lst <> nil then lst^.prev := t1;
  end;
end;
 
procedure sDeleteOdd(var lst: PNode);
var
  t: PNode;
begin
  if lst <> nil then begin
    t := lst;
    lst := lst^.next;
    lst^.prev := nil;
    dispose(t);
    sDeleteEven(lst);
  end;
end;
 
var
  st: pNode;
  e: TElement;
  i: Integer;
 
begin
  st := nil;
  Randomize;
  for i := 1 to 10 do sPush(st, -Random(101) + 50);
  sWrite(st); WriteLn;
  sDeleteOdd(st);
  sWrite(st); WriteLn;
  while st <> nil do sPop(st);
  readln;
end.