A heap-ordered tree structure consisting of n-length subsets of a set. Solutions for the subset sum problem exist in which min-heap trees may be wielded to order all subsets by their sum and then traversed appropriately. By applying a binary search on the list of all sum-ordered subsets, a solution may be found relatively quickly. However, this approach only works for subsets in which all values are positive. The provided code extends this approach to include sets with all values, both positive and negative, by employing a new data structure termed the subset tree.