A new fast algorithm for constructing FP_tree

FP-tree is an efficient algorithm for generating frequent item-sets and the present algorithms are all based on FP_tree generally. But the FP_treepsilas generative process needs much time and it needs to scan database twice. In order to improve the efficiency of constructing the FP_tree, a new fast algorithm called Level FP_tree (abbreviate L-FP_tree) was proposed. The algorithm contains two main parts. Firstly, it scans database and generates equivalence classes of each item. Secondly, it deletes the non-frequent items and rewrites the equivalence classes and then constructs the L-FP_tree.