Easy Strings Question 14 of 224

How do you count the frequency of each character in a string?

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

Walk the string once and increment a hash map or a 26/128-slot array.

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
Walk the string once
and increment a hash map or a 26/128-slot array.
2
Time is O(n) and
space is O(k) for k distinct characters, or O(1) if the alphabet is fixed.
3
This count array is
the building block for anagrams, first-unique, and many hashing problems.
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(k) for k distinct characters, or O(1) if the alphabe”

Break into beats

TimeisOnandspace

Speaking order

2987408337471632900

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

Key takeaway

Walk the string once and increment a hash map or a 26/128-slot array. Time is O(n) and space is O(k) for k distinct characters, or O(1) if the alphabet is fixed.