topological
https://en.wikipedia.org/wiki/Topological_sorting
Test
sbcl --non-interactive --eval "(ql:quickload :topological/tests)" --eval "(asdf:test-system :topological)"
(defparameter *graph-2* '((5 . (11))
(7 . (11 8))
(3 . (8 10))
(11 . (2 9 10))
(8 . (9))))
(top-sort-kahn *graph-2*)
(5 7 3 11 8 10 2 9)
(top-sort-dfs *graph-2*)
(7 3 8 5 11 2 9 10)