Update README.md

The inverted index is not related to graphs but is used in information retrieval

README.md

@@ -105,6 +105,9 @@ Graphs
 
 **Dijkstra’s Algorithm** - Create a program that finds the shortest path through a graph using its edges.
 
+Information Retrieval
+---------
+
 **Inverted index** - An [Inverted Index](http://en.wikipedia.org/wiki/Inverted_index) is a data structure used to create full text search. Given a set of text files, implement a program to create an inverted index. Also create a user interface to do a search using that inverted index which returns a list of files that contain the query term / terms. The search index can be in memory.
 
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@@ -268,4 +271,4 @@ Sources
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 * [Martyr2’s Mega Project List](http://www.dreamincode.net/forums/topic/78802-martyr2s-mega-project-ideas-list/)
-* [Rosetta Code](http://rosettacode.org/)
+* [Rosetta Code](http://rosettacode.org/)