Sorry, but this was a somewhat bad advise. You can solve huge Steiner tree problems (up to a million of edges) in practice to optimality. See for example this s

Sorry, but this was a somewhat bad advise. You can solve huge Steiner tree problems (up to a million of edges) in practice to optimality. See for example this solver: https://scipjack.zib.de/ https://scipjack.zib.de/ There is a wide-spread misconception of the meaning of NP-complete, unfortunately. Also, it should probably be NP-hard, not NP-complete, the latter is for a decision problem only.