← 📦 Data Structures12 / 25
Lesson 12 — Hash maps
Fast lookups
A dict gives O(1) lookups — ideal for counting and dedup.
Task
Find the first repeating character.
Keep going with Data Structures
Ready for more? These paid resources pick up where this lesson leaves off.
UdemyBestsellers
Top-rated Data Structures courses
Project-based Data Structures video courses — the perfect paid next step after these free lessons.
Browse on Udemy →AmazonReader picks
Best Data Structures books
Hand-picked Data Structures books to master the fundamentals offline.
See on Amazon →Some links on this page are affiliate links: we may earn a commission at no extra cost to you. We only recommend tools we believe are genuinely useful.