CareerCup

How about a HashMap where scientist is key and there is a linked list of black_holes for the value if the scientist can query multiple black holes.

And the black_hole can it self contain some information about its identity and a linked list of queries made:

HashMap<Scientist,List<BlackHole>>
Class BlackHole{
	Identity;
	List<Query>;
}

Class Query{
	QueryType;
	QueryResult;
}

I would use a hash with key = scientist id, and a value containing a nested hash with key = black hole id and value = bit map of size 3 (1 bit for each query).

If we look into the problem, it is more like a bipartite graph with n+k vertices. It seems to be most natural to represent it through an adjacency matrix.

It's more like a bidirection many-to-many relationship. Hole and Scientist class should have array of the other type for reference. That means you need to have some sort of manager class to maintain the relationship

// Many-To-Many bidirection
class Hole {
  private id,
  private temperature,
  private radius,
  private size,
  // some getters
  private List<Scientist>,
  public addScientist(Scientist)
}

class Scientist {
  private id, // or name, whatever
  private List<Hole> holes
  public query(holeId) // this calls the QueryManager 
}

class QueryManager {
	private Holes[] // all hole objects
        public Query(int holeId, scientist) // this should find the hole, add the scientist to the array in the hole. return the hole object.
	
}