Dictionary

Dictionary (Data Structure)

Dictionary is a collection of key-value pairs. It is an unordered, mutable, and indexed collection.

In many programming languages, a dictionary is implemented as a hash map.

Dictionary is a data structure that stores key-value pairs. It allows for efficient insertion, deletion, and lookup of values based on their keys.

Operations

1. Add: Insert a key-value pair.
2. Remove: Remove a key-value pair.
3. Get: Get the value associated with a key.
4. Exists: Check if a key exists in the dictionary.

Example

# Create a dictionary
person = {
    'name': 'Alice',
    'age': 30,
    'city': 'New York'
}
 
# Access values using keys
print(person['name'])  # Alice
 
# Add a new key-value pair
person['email'] = 'mail.com`
 
# Remove a key-value pair
del person['city']
 
# Check if a key exists
print('email' in person)  # True

Operations complexity (Time Complexity)

• Add: O(1)
• Remove: O(1)
• Get: O(1)
• Exists: O(1)

Dictionary vs HashMap vs HashTable

• Dictionary: A dictionary is a general term for a data structure that maps keys to values. Map and Associative Array are another terms for a dictionary.
• HashTable: A data structure that implements an associative array abstract data type, a structure that can map keys to values. It uses a hash function to compute an index into an array of buckets or slots, from which the desired value can be found.
• HashMap: A hashmap is a specific implementation of a HashTable. It is generally not synchronized and not thread-safe, making it faster for non-concurrent use cases