Dear all: I have an int list list, whose name is LL and I need to frequently decide whether a particular int list, whose name is L, is a sublist of an element of LL. Is there any efficent data structure to do this? At the mean time, I store LL as (int, bool) Hashtbl.t list, that is, each element of LL is stored as a hash table. So searching L in LL is reduce to decide whether there exist an element of LL, such every element of L hit in this element. At the mean time, the space is not a big problem, but the run time overhead is major concern, So if there exist any more faster data structure? Thank you Shen