26 lines
1.0 KiB
Markdown
26 lines
1.0 KiB
Markdown
# Hash Table
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Well, the moment has come. I never made a Hash Map algorithm, but in this scenario I have to save both fd and sockaddr (
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I could make a simply linked list, but it's a way to learn new things).
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Let's start with a little bit of theory.
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A *Hash Table* is a data structure also called **dictionary** or **map**. It maps *keys* to *values* thanks to a **hash
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function** that computes and *index* (**hash code**) into an array of **buckets**.
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One problem could be the *hash collision* where the hash function computes the same index for different values. A fix
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could be the **chaining** method, where for the same hash code you can make a linked list and append the index. Then the
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lookup function will go through the list and find the key.
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In a Hash Map you can insert, delete and lookup (simply search).
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### Hash function
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The easiest way... don't judge me.
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- Integer keys:
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$$ hash(\text{key}) = \text{key} \mod \text{table\_dim} $$
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- String keys:
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$$ hash(key) = \sum_{i=0}^{len(key) - 1} ascii\_value(key[i]) * prime\_number$$
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