;; figure 3.12
(defun shortest-path (start end net)
	(bfs end (list (list start)) net ))
	
(defun bfs (end queue net)
	(if (null queue)
		nil
		(let ((path (car queue))) ; this will be list
			(let ((treenode (car path))) ; car of the list
				(if (eql treenode end) ; if t we've found a shortest path (could be more)
					(reverse path) ; path built from cons, need to reverse 
					(bfs end
						(append (cdr queue)
								(new-paths path treenode net))
						net))))))

(defun new-paths (path treenode net)
	(mapcar #'(lambda (n)
				(cons n path))
			(cdr (assoc treenode net)))) ; find other nodes we can reach from node
			
(deftest test-binary-search()
	(let ((net '((a b c) (b c) (c d))))
	(check
		(equal '(a c d) (shortest-path 'a 'd net)))))