i am thinking for compressing row with reduce the size of dataset...

first at one part transactions are given and i have to fixed size of transaction.and in other part itemsets and size of itemsets are given,,,than how it work???
so it's work is suppose if itemset is is 3 then it is finding in datasetin that which dataset size is greater then or equal to 3..


plz give me a idea about in c++ how to implement it in that...