A Java / Gradle TDD project. The demo class makes use of some Java 8 features i.e. Stream & Lambdas

Optimise lookup by Author & Title.

Internally this is a HashMap<String, Set<String>>

• key: author name String. This utilises the built in String hashing function to provide a O(n) time complexity for lookups
• value: set of titles HashSet<String>. This enables title entries to be removed with O(n) complexity

Internally this is also a HashMap<String, Set<String>> with keys and value reversed compared to the previous index.

• key: book title String. This utilises the built in String hashing function to provide a O(n) time complexity for lookups
• value: author name HashSet<String>. This enables name entries to be removed with O(n) complexity

Each add operation will update both:

1. Author to Titles Index
2. Title to Authors Index

Each remove operation will also update both:

1. Author to Titles Index
2. Title to Authors Index

NOTE : Removing authors will also remove co-authors for the title