Count partitions and equal-cost packages

Question

Given a string itemCategories, count the number of ways to partition it into exactly two contiguous non-empty substrings (a prefix and a suffix) such that the number of distinct characters appearing in both substrings is greater than k. Given an array itemCosts representing item costs, determine the maximum number of packages that can be created so that each package contains at most two items, all packages have the same total cost, and each item is used in at most one package.