绘制所有子节点公共Lisp的图

Question

I need to find all nodes that are children of selected node. Graph is created like this: (setq graf1 '((A(BC)) (B(DE)) (C (FG )) (D (H)) (E(I)) (F(J)) (G(J)) (H()) (I(J)) (J()))) So, all children from node B are (on first level) D,E, on 2nd H,I, third J. Here's the code for finding first level children, but as i'm begineer in lisp i cant make it work for other ones.

(defun sledG (cvor graf obradjeni)
  (cond ((null graf) '())
        ((equal (caar graf) cvor)
                (dodaj (cadar graf) obradjeni))
        (t(sledG cvor (cdr graf) obradjeni)))
(defun dodaj (potomci obradjeni)
  (cond ((null potomci) '())
        ((member (car potomci) obradjeni)
         (dodaj (cdr potomci) obradjeni )
        (t(cons (car potomci)
                (dodaj (cdr potomci) obradjeni) ))))
(setq graf1 '((A(B C)) (B(D E)) (C (F G )) (D (H)) (E(I)) (F(J)) (G(J)) (H()) (I(J)) (J())))

Answer 1

As I read it, the graph is a directed graph. So to find the children (directed edges) of the graph (in the example),

(defun children (node graph) (second (assoc node graph)))

then

(children 'b graf1) ; with graf1 from the OP

returns (DE). All you have to do then is to loop over the children, something like (very quick and dirty)

(defun all-children (node graph)
  (let ((c (children node graph)))
    (if (null c) nil
        (union c (loop for x in c appending (all-children x graph))))))

This returns (JIHDE) as children of B.

Answer 2

Using alexandria package:

(defvar *graf*
  '((a (b c)) (b (d e)) (c (f g)) (d (h)) (e (i)) (f (j)) (g (j)) (h nil) (i (j)) (j nil)))

(defun descendants (tree label)
  (let ((generation
         (mapcan #'cadr
                 (remove-if-not
                  (alexandria:compose (alexandria:curry #'eql label) #'car)
                  tree))))
    (append generation (mapcan (alexandria:curry #'descendants tree) generation))))

;; (D E H I J)

I believe, this is what you wanted to do. This will work for acyclic graphs, but it will recur "forever", if you have a cycle in it. If you wanted to add depth counter, you could add it as one more argument to descendants or in the last mapcan transform the resulting list by inserting the depth counter.

With depth included:

(defun descendants (tree label)
  (labels ((%descendants (depth label)
             (let ((generation
                    (mapcan #'cadr
                            (remove-if-not
                             (alexandria:compose
                               (alexandria:curry #'eql label) #'car)
                             tree))))
               (append (mapcar (alexandria:compose
                                #'nreverse
                                (alexandria:curry #'list depth))
                               generation)
                       (mapcan (alexandria:curry #'%descendants (1+ depth))
                               generation)))))
    (%descendants 0 label)))

;; ((D 0) (E 0) (H 1) (I 1) (J 2))