Easy Sliding Window Question 26 of 224

How do you find the maximum sum of any contiguous subarray of length k?

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

Sum the first k elements, then slide: add the incoming element and subtract the leaving one, tracking the max.

WHY — Sliding Window instead of guessing?

Why interviewers care about Sliding Window:

This is a process

question about Sliding Window.

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
Sum the first k
elements, then slide: add the incoming element and subtract the leaving one, tracking the max.
2
After the first window
each step is O(1), so total time is O(n) with O(1) extra space.
3
Recomputing each window from
scratch would be O(nk), which you should call out as too slow.
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.

EXAMPLE — See it in action

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

Say this line

“After the first window each step is O(1), so total time is O(n) with O(1) extra ”

Break into beats

Afterthefirstwindoweachstep

Speaking order

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

Key takeaway

Sum the first k elements, then slide: add the incoming element and subtract the leaving one, tracking the max. After the first window each step is O(1), so total time is O(n) with O(1) extra space.