juniorStrings

How to reverse a string in-place?

Updated Apr 28, 2026

Short answer

Swap characters from the beginning and end moving towards the middle (requires mutability).

Deep explanation

Strings are one of the most common data types. Swap characters from the beginning and end moving towards the middle (requires mutability). Understanding how they are represented (ASCII/UTF-8/UTF-16) is key to solving character encoding issues.

Real-world example

Storing user names or IDs in an application.

Common mistakes

  • Modifying a string inside a long loop without using a StringBuilder/StringBuffer.

Follow-up questions

  • What is the time complexity of concatenation?

More Strings interview questions

View all →