Easy Arrays Question 8 of 224

How do you compute the union of two unsorted arrays without duplicates?

DSA interview set · Speak this in 60–90 seconds · Faridabad & Delhi NCR

01234

Index starts at 0. Scan once for max — O(n).

Insert every element of both arrays into a hash set, then dump the set into a list.

Why interviewers care about Arrays:

This is a process

question about Arrays.

Panels listen for order,

trade-offs, and what you would actually do on a DSA project - not buzzwords.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

End with when you use it and one common pitfall.

Before you speak the answer, walk the interviewer through these steps:

1
Insert every element of
both arrays into a hash set, then dump the set into a list.
2
Average time is O(n+m)
with O(n+m) space.
3
Sorting both and merging
unique values is O((n+m) log(n+m)) and uses less hashing, which is a good follow-up.
4
Give an example
One tiny concrete case you can say aloud.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

Here's a short line you can speak, broken into clear beats:

Say this line

“Average time is O(n+m) with O(n+m) space.”

Break into beats

AveragetimeisOnm

Speaking order

2987408337471632900

Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

Insert every element of both arrays into a hash set, then dump the set into a list. Average time is O(n+m) with O(n+m) space.