CODEWITHSUNDEEP
javajava-7
Gil Peretz
Gil Peretz

Reputation: 2419

Java7 Cartesian Product versia without duplicates

Assuming I have a set<Integer> (few thousands). I want to perform cartesian product but without any duplicates.

A duplicate entry is considered to have the inverse element in the set (i.e. <1,3> and <3,1> are considered duplicates).

How can I do it efficiently?

First I use Sets.cartesianProduct(set, set) which results ~22M elements, but it also contained duplications. iterating that list again to check result.contains(..) is not efficient at all.

Upvotes: 0

Views: 326

Answers (1)

Gil Peretz
Gil Peretz

Reputation: 2419

Funny, I've been messing around with this for few hours, and the moment I write a question in Stackoverflow, I suddenly realize the answer myself ;)

Edited following @DmitryGorkovets improvement 

for (int i = 0; i < list.size(); i++) {
    for (int j = i+1; j < list.size(); j++) {
        result.add(new Pair<>(list.get(i), list.get(j)));
    }
}

Upvotes: 1

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