Hash Map: Collision Handling
Visualize how internal Hash Tables work! See how keys are hashed to indices and how collisions are resolved using Chaining (Linked Lists).
Hash Map (Separate Chaining)
Visualize how a hash map stores key-value pairs and resolves collisions by chaining multiple entries in the same bucket.
put(key, value) with chaining
Order what a chained hash map does on insert.
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Test your knowledge
What is the worst-case time complexity of searching in a Hash Map with Chaining?
Write the code
Two Sum
The short version
Think of a library where every book has a specific shelf determined by a formula based on its title. You don't browse; you calculate the exact location and go straight there.
In more depth
Constant Time Magic
A Hash Map (or Hash Table) allows for O(1) average time complexity for Insert, Delete, and Lookup. It works by using a Hash Function to map a key (like a string) to an index in an array.
Collisions:
When two keys map to the same index.
Hash Maps are the single most useful data structure in interviews for trading space for time.
When to reach for this
- Count frequency of elements
- Check existence in O(1)
- Map a key to a value (Caching)
Interview Questions
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