Introduction

In software development, dictionaries (or maps) are often used to facilitate fast lookups between keys and values. Sometimes, applications require mapping in both directions, which a typical dictionary does not naturally support because lookups inherently favor one direction - from a key to a value. This article explores how a Bidirectional 1-to-1 Dictionary can be implemented in C#, providing an efficient way to access elements in both directions while ensuring bijective relationships.

Concept of a Bidirectional Dictionary

A bidirectional dictionary ensures a one-to-one mapping between two sets of data, allowing for lookup in either direction without the need for duplicate data structures. This means that given a key, you can find a corresponding value, and given a value, you can find its associated key.

Key Characteristics:

• Bijective Mapping: Every key has a unique value, and every value has a unique key.
• Constant Time Complexity: Both key-to-value and value-to-key lookups should ideally have O(1) access time.
• Synchronous Update: Changes in one direction should reflect immediately in the other direction.

Implementation in C#

Primary Data Structures

To implement a bidirectional dictionary in C#, we can utilize two dictionaries: one for the key-to-value mapping and another for the value-to-key mapping. Below is an example implementation:

• Add(T1 key, T2 value): This method establishes a mapping between a key and a value in both directions while ensuring no duplicates exist.
• GetValue(T1 key) and GetKey(T2 value): Both methods retrieve elements in constant time, enabling efficient lookups.
• RemoveByKey(T1 key) and RemoveByValue(T2 value): These methods remove the mapping in both dictionaries, keeping data consistent.
• Count: This property returns the number of elements in the dictionary, mirroring both maps.
• Text Processing: Mapping between words and identifiers or codes.
• Systems with Inverse Relationships: Associating foreign language words with their native translations.
• Data Synchronization: Keeping corresponding data elements in sync.