s to s: s   weight 0 (d = 0)  OK
s to u: s -> x -> u   weight 8 (d = 8)  OK
s to v: s -> x -> u -> v   weight 9 (d = 9)  OK
s to x: s -> x   weight 5 (d = 5)  OK
s to y: s -> x -> y   weight 7 (d = 7)  OK
s to q: unreachable

the recursive PRINT-PATH, for comparison:
  s
  s -> x -> u
  s -> x -> u -> v
  s -> x
  s -> x -> y
  no path from s to q
