Question

I have an ordered list A and a string set B in Java. I need the comparision output to be in the form of a binary array. For example if A was {a,b,c,d,e} and B was {a,d,e}, my output should be an array [1,0,0,1,1]. How can i achieve this efficiently without resorting to brute force checking? I’m dealing with quite a large number of sets(large in size too) to compare with A.

Answer 1

What sort of sets are these? Normally sets don’t have any order.

It feels like essentially we need to treat B as a set but A as a list. For example, you might use:

List<String> a = ...;
Set<String> b = ...;

boolean result = new boolean[a.size()];
for (int i = 0; i < result.length; i++) {
  result[i] = b.contains(a);
}

So long as the set implementation is a fast one (e.g. HashSet or LinkedHashSet) this should be an O(n) operation where n is the size of a. It’s hard to see how you could do significantly better given that you need to produce n results…