IMHO, calculating the resulting resistance of all pairs is the most resource intensive process. Depending on whether you allow the user to perform multiple searches, it may make sense to precalculate them once and sort by the result to easily find the matching pairs. This precalculation can be performed during the construction of the class object, where the list of available resistors is passed to initialize it.
So maybe just store the pre-computed values in the class and have a class method return the list of matching pairs instead of storing them in the object. WDYT?
