The Apriori algorithm uses a hash tree data structure to effrciently count the s

Question

The Apriori algorithm uses a hash tree data structure to effrciently count the support of candidate itemsets. Consider the hash tree for candidate 3-itemsets shown in Figure

(a) Given a transaction that contains items {1,3,4,5,8}, which of the hash
tree leaf nodes will be visited when fi.nding the candidates of the transaction?
(b) Use the visited leaf nodes in part (b) to determine the candidate itemsets
that are contained in the transaction {1,3,4,5,8}.

1,4,7 1,4,7 3,6,9 1,4,7 3,6,9 2,5,8 1,4,7 3,6,9 2,5,8 (346) 356) (367) (678) 2,5,8 L11 L1 L5 L6 ?7 ?12 f145) (178 1,4,7 /2,5,8 (246 (258)1379(689) (278 (289) 3,6,9 ?2 ?3 ?4 (127 125 1459) (457) (158) (456) 458) (789)

Explanation / Answer

a) The leaf nodes visited are L1, L3, L5, L9, and L11.

b) The candidates itemsets contained in the transaction are {1, 4, 5}, {1, 5, 8}, and {4, 5, 8}.

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