(defun validate-dp (password words)
  (let ((v (make-array (1+ (length password)) :initial-element nil)))
    (setf (aref v 0) t)
    (loop for i upto (length password) do
      (loop for w in words do
        (let ((lw (length w)))
          (if (and (<= lw i) (string= w (subseq password (- i lw) i)) (elt v (- i lw)))
            (setf (aref v i) w)))))
    (if (aref v (- (length v) 1))
      (coerce (remove nil (remove T v)) 'list)
      nil)))