Question

Inverted Index is a one big HashMap with A. key as the token and value as the document that contains that token B. key as the token and value as the list of documents with contains that token C. key as the document and value as all the tokens in that document D. none of the above

Answer 1

B. key as the token and value as the list of documents with contains that token

Explanation:

An inverted index is an index data structure storing a mapping from content, such as words or numbers, to its locations in a document or a set of documents. In simple words, it is a hashmap like data structure that directs you from a word to a document or a web page.

There are two types of inverted indexes: A record-level inverted index contains a list of references to documents for each word. A word-level inverted index additionally contains the positions of each word within a document. The latter form offers more functionality, but needs more processing power and space to be created.
Suppose we want to search the texts “hello everyone, ” “this article is based on inverted index, ” “which is hashmap like data structure”. If we index by (text, word within the text), the index with location in text is:

 hello                (1, 1)
 everyone             (1, 2)
 this                 (2, 1)
 article              (2, 2)
 is                   (2, 3); (3, 2)
 based                (2, 4)
 on                   (2, 5)
 inverted             (2, 6)
 index                (2, 7)
 which                (3, 1)
 hashmap              (3, 3)
 like                 (3, 4)
 data                 (3, 5)
 structure            (3, 6)

The word “hello” is in document 1 (“hello everyone”) starting at word 1, so has an entry (1, 1) and word “is” is in document 2 and 3 at ‘3rd’ and ‘2nd’ positions respectively (here position is based on word).
The index may have weights, frequencies, or other indicators.