A system determines a count of each item in each item set, sorts each count into ascending order, assigns an ascending identifier to each item corresponding to each sorted count, and sorts each identifier in each item set in descending order. The system partitions item sets into a first group of item sets and a second group of item sets, each item set in the first group including a common largest identifier, determines a count for each subset of each item set of the first group, and determines a count of each subset of each item set by summing each count for each subset of each item set of the first group with each corresponding count for each corresponding subset of each item set of the second group. The system outputs a recommended item set based on the count of each subset of each item set.