- ... tree.
^{1} - The
reader may wonder why this simpler algorithm was not presented before the
more complicated algorithm solve_constraints. The reason is that
the only proof we have found that the system of constraints is consistent
if num_labels does not return
**false**relies on the relation between num_labels and the constructive solve_constraints.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .