稍加修改

• However , it suffers from great complexity and low efficiency . the hash - tree - based approach is a slight modification of the apriori algorithm , which , again , we find not satisfying . to further improve the efficiency , we devise another approach based on a different yet similar tree structure
  第一种算法是从混合规则的定义出发采用直接的方法生成大项集，算法的复杂度较大，效率不高；第二种算法是对apriori算法稍加修改得到的，也不够令人满意；为进一步提高执行效率，我们设计了基于一种树结构的算法。