An “inverted file” is a critical data structure for implementing applications like the index of a book, or a web search engine.  Given a document D (which can be viewed as an unordered, numbered list of words), an inverted file is an ordered list of words L such that for each word W in L, we store the indices of the places in D where W appears.  Write a C# program (from scratch please, written by yourself (ask instructor if you are stuck), not borrowed from any other sources) that reads in a list of words separated by spaces from a text file, then uses an efficient O(N) algorithm to create the inverted file index (hint: consider the topic of this chapter, consider using a Dictionary/hashtable to help you), and writes this index out to another file or prints it to the screen.  Each line of the output file should start with the next word (the words should be listed in alphabetical order, and this sorting does not have to be part of the O(N) runtime complexity, e.g. you can use regular O(N log N) complexity sorting algorithms), then the rest of the line should contain a sequence of integers, representing the indexes where that word appeared in the original input text file.  (Assume the index of the first word in the original file is zero.)   You can consider punctuation to be part of the word (so for example, “hello” and “hello!” would be considered different words). Example input file: Hello world hello world hello Output file: hello 2 4 Hello 0 world 1 3

An “inverted file” is a critical data structure for implementing applications like the index of a book, or a web search engine.  Given a document D (which can be viewed as an unordered, numbered list of words), an inverted file is an ordered list of words L such that for each word W in L, we store the indices of the places in D where W appears.  Write a C# program (from scratch please, written by yourself (ask instructor if you are stuck), not borrowed from any other sources) that reads in a list of words separated by spaces from a text file, then uses an efficient O(N) algorithm to create the inverted file index (hint: consider the topic of this chapter, consider using a Dictionary/hashtable to help you), and writes this index out to another file or prints it to the screen.  Each line of the output file should start with the next word (the words should be listed in alphabetical order, and this sorting does not have to be part of the O(N) runtime complexity, e.g. you can use regular O(N log N) complexity sorting algorithms), then the rest of the line should contain a sequence of integers, representing the indexes where that word appeared in the original input text file.  (Assume the index of the first word in the original file is zero.)   You can consider punctuation to be part of the word (so for example, “hello” and “hello!” would be considered different words).

Example input file:

Hello world hello world hello

Output file:

hello 2 4

Hello 0

world 1 3