The type of hetrogenous key sets.

O(1) Construct an empty key set.

O(1) Construct a set with a single element.

O(n+m) Construct a key set containing all elements from both sets.

To obtain good performance, the smaller set must be presented as the first argument.

Construct a key set containing all elements from a list of key sets.

O(1) Return True if this key set is empty, False otherwise.

O(n) Return the number of elements in this set.

O(min(n,W)) Return True if the given value is present in this set, False otherwise.

O(min(n,W)) Add the specified value to this set.

O(min(n,W)) Remove the specified value from this set if present.

O(n) Difference of two sets. Return elements of the first set not existing in the second.

O(n) Intersection of two sets. Return elements present in both the first set and the second.

O(n). Does the map carry any of the keys?

O(n). Do the keyset and the map have the same keys?

O(n). Remove the keys from the keyset from the map.