Choosing Between HashMap and HashSet
Most programming languages have types like HashMap (also known as Dictionary, Hashtable or map) and HashSet (also known as set). The map types can store both a key and a value, and the set types just store a key. No duplicate keys are allowed—these collections check for uniqueness.
It seems like it is common sense to do certain things with a map, and other things with a set. But is this really necessary? It is possible to do everything with just the map types, and never use the set types. We can just use any value—like a bool with the value true, or the integer 1.
In any case, we typically use sets when:
Intersect or Overlaps are required.In my experience, normal programs rarely require mathematical set operations. And it makes about as much sense just to use true to indicate a value instead of using an entirely different type like HashSet. There is no likely performance impact. If we are using a Dictionary elsewhere, it may reduce code size to reuse that class for set operations, however.