Convert HashMap of integers into unique integer array?

Asked Apr 20 '14 at 22:18

Active Apr 20 '14 at 22:18

Viewed 47 times

How can I take the information stored in a HashMap<Integer, ArrayList<Integer>> and create unique arrays of values. I do not need them in reverse order or any other ordering.

For example, assuming I have:

Key      Value
---      ---------
1        {1, 2, 3}
2        {10, 11}
3        {29}

How can I turn this into the following:

{1, 10, 29}
{1, 11, 29}
{2, 10, 29}
{2, 11, 29}
{3, 10, 29}
{3, 11, 29}

Ive tried a variety of loops. I also pondered tail end recursion however it still has me stumped. I would appreciate your guidance so I may solve this.

What my goal is: The key value is the primary key for an attribute. Each attribute has options which are contained in the value. I would like to restructure the information so it fits the format shown.

asked Apr 20 '14 at 22:18

medokr

This is what `Set` implementations are for. – Apr 20 '14 at 22:20
Jarrod, thanks for the response. I will start researching Set implementations. – medokr Apr 20 '14 at 22:21
@JarrodRoberson: I don't think a `Set` is a specific solution here. The title is rather irrelevant to the problem: he's looking for all permutations that hold one value from each key. – Jeroen Vannevel Apr 20 '14 at 22:23
3

You are asking for how to generate the *cartesian product*. There are countless duplicates here on SO. – Oliver Charlesworth Apr 20 '14 at 22:25
Oli, after researching what a cartesian product is, I agree with duplicate. Thanks for hinting at solution. – medokr Apr 21 '14 at 15:26

Convert HashMap of integers into unique integer array?

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