Easy Strings Question 15 of 224

How do you check if one string is a rotation of another?

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

Train 70%Val 15%Test 15%

Fit on train, tune on val, report on test once.

Equal length is required.

Why interviewers care about Strings:

This is a process

question about Strings.

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
Define it
Equal length is required.
2
Concatenate the first string
with itself and test whether the second is a substring of that doubled string.
3
Building the double is
O(n) time and O(n) space
4
substring search is O(n)
with KMP or O(n^2) naive, which you should name.
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

“Concatenate the first string with itself and test whether the second is a substr”

Break into beats

Concatenatethefirststringwithitself

Speaking order

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

Equal length is required. Concatenate the first string with itself and test whether the second is a substring of that doubled string.