Скачать или смотреть Секретное оружие LeetCode 🔑 Шаблон HashMap

Are you still using for loops to find one user in a million? That might be the #1 reason your code is slow and why you're struggling in coding interviews. In this video, we're unlocking LeetCode's secret weapon: The HashMap and HashSet Data Structures, the key to O(1), or instant, access.

This isn't just a theory lesson. Through real-world analogies (like a library catalog and a VIP guest list) and practical code examples, you'll master the logic behind these fundamental data structures and learn how to use them to solve problems efficiently.

📚 In this video, you will learn:

The Concept: Why a HashMap works just like a Library Catalog for instant lookups.

Use Case 1: The Frequency Counting Pattern (Code Example).

Use Case 2: The Instant Lookup Pattern (Classic "Two Sum" Problem).

The Key Difference: HashMap vs. HashSet? When to use which?

The HashSet Concept: Why it's like a VIP Guest List for unique items.

HashSet in Action: The most elegant solution to the "Contains Duplicate" problem.

This video is the most important foundation you need before we start our Amazon Interview series!

🔔 If you enjoyed this video, don't forget to subscribe, like, and share for more advanced Java 21 content and coding patterns!

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💬 Answer in the comments: In which type of problem do you use HashMaps or HashSets the most?