Easy Strings Question 9 of 224

How do you reverse a string if it is stored as a mutable character array?

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

Two pointers swap from both ends until they meet, which is O(n) time and O(1) extra space.

WHY — Strings instead of guessing?

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.

STEPS — What happens step by step?

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

1
Two pointers swap from
both ends until they meet, which is O(n) time and O(1) extra space.
2
In languages where strings
are immutable you allocate a new string, still O(n) time and O(n) space.
3
Call out immutability so
you do not claim in-place on Python str.
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

“In languages where strings are immutable you allocate a new string, still O(n) t”

Break into beats

Inlanguageswherestringsareimmutable

Speaking order

2987408337471632900

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

Key takeaway

Two pointers swap from both ends until they meet, which is O(n) time and O(1) extra space. In languages where strings are immutable you allocate a new string, still O(n) time and O(n) space.