Easy Two Pointers Question 24 of 224

How do you test a palindrome while ignoring non-alphanumeric characters and case?

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.

Two pointers skip non-letters/digits, compare lowercased characters, and stop on mismatch.

Why interviewers care about Two Pointers:

This is a process

question about Two Pointers.

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
Two pointers skip non-letters/digits,
compare lowercased characters, and stop on mismatch.
2
Time is O(n) and
extra space is O(1).
3
Building a filtered copy
is clearer but O(n) space
4
interviewers like the in-place
skip version.
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

“Time is O(n) and extra space is O(1).”

Break into beats

TimeisOnandextra

Speaking order

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

Two pointers skip non-letters/digits, compare lowercased characters, and stop on mismatch. Time is O(n) and extra space is O(1).