Moderate Strings Question 77 of 224

How would you implement atoi, converting a string to a 32-bit signed integer?

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

PICTURE THIS: HOW TO EXPLAIN IT

IdeaStrings

HowWhat happens inside

Why they askShows real use

Simple meaning

Skip leading spaces, read an optional sign, then accumulate digits while checking overflow against INT_MAX/MIN before multiplying by 10.

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
Skip leading spaces, read
an optional sign, then accumulate digits while checking overflow against INT_MAX/MIN before multiplying by 10.
2
Time is O(n) and
space is O(1).
3
Clamp on overflow as
the problem requires, and stop at the first non-digit after the number starts.
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

“Time is O(n) and space is O(1).”

Break into beats

TimeisOnandspace

Speaking order

2987408337471632900

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

Key takeaway

Skip leading spaces, read an optional sign, then accumulate digits while checking overflow against INT_MAX/MIN before multiplying by 10. Time is O(n) and space is O(1).