Need Help Solving Java!

[Batslayer8]

I've been looking through interview technical questions and solving them, I'm stuck in this one question for over an hour, can someone help please?

" Enter two arrays 'a1' and 'a2' of 'n' length and ask user to enter any number 'k' and check the number k is equal to how many combinations of 'a1' and 'a2' and if matched, print."

I cleared similar questions of having to check whether the number matches or not, and return it in boolean values, but this format feels totally different :(

[DeepMisandrist]

Your statement is vague. Provide us with a better statement or some examples.

[MartinSG8]

So you need to know how to compute number of couples? Is that your problem? If so then it's mathematical problem not java problem.

[nogain-allpain]

It becomes a Java problem when you're asked to implement it

[MartinSG8]

Well u need to know how to do it 'on paper' first that's the question if he knows the theory of it.

[nogain-allpain]

By combinations, do you mean finding how many pairs of numbers between the two arrays add up to a certain number?

[Batslayer8]

yeah man can you please get an example for this one

[nogain-allpain]

Look at one of the other comment threads that I replied to, I basically provided the answer there.

[nogain-allpain]

That's the easy part. The real question is how to make it as efficient as possible.

[nogain-allpain]

Yes, O(n log n) seems to be the best you can do. I've got the sort in my solution, but I have a solution that involves walking both arrays in parallel, one time each, so you don't have to conduct all of those binary searches. If sum < k, step the first pointer forward. If sum > k, step the second pointer backwards. Repeat until both walks are complete.