Need to generate superset in java

问题

Trying to figure out a way to generate a superset using java need simple answer to

what am looking for is

Input : ab

Output : {} {a} {b} {ab}

how do i go about this any clue ?

Thanks in advance

回答1:

int allMasks = (1 << N);
for (int i = 1; i < allMasks; i++)
{
    for (int j = 0; j < N; j++)
    if ((i & (1 << j)) > 0)           //The j-th element is used
        System.out.print((j + 1) + " ");

    System.out.println();
}

回答2:

Since this is currently the second result in google for java superset I'm going to answer that query.

Set.addAll will do this.

example:

// A couple of sets
Set<Integer> set1 = new TreeSet<>(Arrays.asList(1, 2));
Set<Integer> set2 = new TreeSet<>(Arrays.asList(2, 3));

// Generate the superset    
Set<Integer> superset = new TreeSet<>();
superset.addAll(set1); // {1, 2}
superset.addAll(set2); // {1, 2, 3}

来源：https://stackoverflow.com/questions/21620006/need-to-generate-superset-in-java