What is the role and application of hash tables in programming?

Hash tables are data structures that provide very fast access to elements by key, usually in near O(1) time.

The main idea: the key is transformed using a hash function into an array index where the value is stored.

Role and applications:

• Fast search, insertion, and deletion of data by key.
• Used for implementing dictionaries, caches, sets.
• In Python, the dictionary (dict) is an implementation of a hash table.

Example of using a dictionary in Python:

phone_book = {
    "Ivan": "+71234567890",
    "Maria": "+79876543210"
}

print(phone_book["Ivan"])  # Outputs: +71234567890

Hash tables are efficient when you need to quickly find data by a unique key, making them indispensable in programming.