Strings

9 problems · Easy to Medium · String patterns and sliding window

String problems test your ability to manipulate character sequences efficiently and recognize when a sliding window can reduce complexity. This track covers foundational problems like palindrome and anagram detection before moving into substring search with KMP and variable-size sliding window problems like Longest Repeating Character Replacement.

Why it matters:

Strings are the second most common interview topic after arrays, and companies like Amazon and Microsoft use them heavily in phone screens. The sliding window pattern introduced in this track recurs across dozens of problems involving subarrays and subsequences — learning it here pays dividends throughout the rest of the course.

Strings

9 problems · Easy to Medium · String patterns and sliding window

Why it matters:

Valid Palindrome - A Warm Up

Valid Anagram

First Unique Character in a String

Longest Common Prefix

Needle In a Haystack - Part 1

Longest Substring Without Repeating Characters

Minimum Size Subarray Sum

Longest Repeating Character Replacement

Deriving KMP in Real Time