addElt:
	A: add the element O(1)
	B: check to see if the element exists, and then add O(n)
removeElt:
	A: remove all instances of that element from the list O(n)
	B: remove the first and only instance O(n)
hasElt: element -> boolean
	A: search the list and return the first instance found or false if not found O(n)
	B: same as A O(n)
size: set -> integer
	A: count number of unique elements O(n^2)
	B: count number of elements O(n)