10: Sets

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Sets are helpful tools in a software application where, just as in mathematics, similar abstract objects are aggregated into collections. A mathematical set has a fairly simple interface and can be implemented in a surprising number of ways.

Set<item-type> ADT

contains(test-item:item-type):Boolean

True if test-item is contained in the Set.

insert(new-item:item-type)

Adds new-item into the set.

remove(item:item-type)

Removes item from the set. If item wasn't in the set, this method does nothing.

remove(item-iter:List Iterator<item-type>)

Removes the item referred to by item-iter from the set.

get-begin():List Iterator<item-type>

Allows iteration over the elements in the Set.

get-end():List Iterator<item-type>

Also allows iteration over the elements in the Set.

union(other:Set<item-type>):Set<item-type>

Returns a set containing all elements in either this or the other set. Has a default implementation.

intersect(other:Set<item-type>):Set<item-type>

Returns a set containing all elements in both this and the other set. Has a default implementation.

subtract(other:Set<item-type>):Set<item-type>

Returns a set containing all elements in this but not the other set. Has a default implementation.

is-empty():Boolean

True if no more items can be popped and there is no top item.

get-size():Integer

Returns the number of elements in the set.

All operations can be performed in \(O(N)\) time.