Moderate Arrays Question 71 of 224

How do you compute the product of every array element except itself without using division?

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

PICTURE THIS: ARRAY IN MEMORY

01234

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

Simple meaning

Build prefix products to the left of i and suffix products to the right of i, then multiply those two for each index.

WHY — Arrays instead of guessing?

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.

STEPS — What happens step by step?

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

1
Build prefix products to
the left of i and suffix products to the right of i, then multiply those two for each index.
2
Two extra arrays are
O(n) time and O(n) space
3
you can store prefixes
in the output and then fold suffixes in a second reverse pass for O(1) extra space besides the answer.
4
Division fails on zeros
and is usually banned.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

EXAMPLE — See it in action

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

Say this line

“Two extra arrays are O(n) time and O(n) space”

Break into beats

TwoextraarraysareOn

Speaking order

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

Key takeaway

Build prefix products to the left of i and suffix products to the right of i, then multiply those two for each index. Two extra arrays are O(n) time and O(n) space