Suppose that we are using the Apriori algorithm to generate frequent itemsets and that we use hash trees to facilitate the support counting of candidate itemsets. Assume that the length-4 candidate itemsets are: {1, 2, 4, 5}, {1, 2, 5, 7}, {1, 2, 6, 8}, {1, 3, 4, 5}, {1, 3, 6, 7}, {1, 4, 6, 8},

{1, 5, 6, 7}, {2, 3, 4, 7}, {2, 4, 5, 6}, {3, 4, 5, 7}, {3, 5, 6, 8}, {3, 5, 7, 8}, {4, 5, 7, 8} where a number in a set is an item id.

1. Which leaf node(s) in the hash tree are visited when trying to find all the length-4 candidates contained in t ? You can answer this question by marking the leaf node(s) that are visited with square(s) in the tree that you drew for part (a).