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Technical Interview Prep: Hash Tables

Hash tables: What are they and how do they work?

Searching is made easier by hash tables.

The structure of a hash table consists of three parts:

  • Arrays
  • Linked-lists
  • Hashing-functions

In a hash table, the hashing function transforms the key. Keys are pieces of data that are converted into array indexes via the hash function.

Due to the fact that the array index is used to speed up lookup, this is necessary.

The hash table is then derived from the array index.

Hash tables: When do you need them?

Hash tables are good for constant-time lookups, insertions, and deletions.

It is not recommended to store sorted data in hash tables.

  • Searches, insertions, and deletions are optimized in hash tables.
  • Hash collisions occur when two distinct inputs yield the same output of a hash function. These are inherent problems of hash functions.
  • Hash tables are used to create symbol tables and index databases.

With a hash table, you can calculate memory

Sets, objects, and dictionaries are among the things that use hash tables in coding languages.

Dictionary and set concepts are used in Python. Sets and objects are also available in JavaScript.

The memory usage of a hash table may vary greatly depending on the language.

You should use a fixed-size array when creating a hash table most of the time. Linked lists are best for storing data.

Hash Table Operations

  • Inserting key-value pairs
  • Finding a key's value
  • Updating a key's value
  • Seeing if a key is already used
  • Looping over key-value pairs
  • Deleting key-value pairs
  • Searching for values