Moderate Two Pointers Question 87 of 224

How do you check whether string s is a subsequence of string t?

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

IdeaTwo Pointers

HowWhat happens inside

Why they askShows real use

Walk t with a pointer into s

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
Walk t with a
pointer into s
2
advance the s pointer
whenever characters match.
3
If the s pointer
reaches len(s), it is a subsequence.
4
Time is O(len(t)) and
space is O(1).
5
For many s queries
against one t, preprocess next-occurrence tables in O(len(t) * alphabet).
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(len(t)) and space is O(1).”

Break into beats

TimeisOlentand

Speaking order

2987408337471632900

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

Walk t with a pointer into s advance the s pointer whenever characters match.