// Copyright 2015, University of Freiburg,
// Chair of Algorithms and Data Structures.
// Author: Hannah Bast <bast@cs.uni-freiburg.de>.

// NOTE: this file contains specifications and design suggestions in
// pseudo-code. It is not supposed to be compilable in any language. The
// specifications are mandatory, the design suggestions are not.

// Class for a simple inverted index.
class InvertedIndex

  // Construct from given text file (one record per line). This method was
  // coded during lecture 1, using Python.
  void build_from_file(String file_name)

  // Merge two inverted lists (= sorted lists of record ids). Take proper care
  // of duplicates. For example, the merged result of 1, 3, 3, 4, 6 and 2, 3, 
  // 5, 7, 7 is 1, 2, 3, 3, 3, 4, 5, 6, 7, 7. Alternatively, you may also
  // represent each list item as a pair (record id, count).
  Array<int> merge(Array<int> list1, Array<int> list2)

  // Process a given keyword query. For each keyword, fetch the corresponding
  // inverted list. Merge using repeated calls to the method above,
  // that is: Merge the first two keywords, then merge the result list 
  // with the list for the third keyword, and so on.
  //
  // Return a list of pairs (record id, count), where count = sum_i ki if the
  // i-th keyword matches the record in ki places, sorted by count. If the query
  // is empty, or there are no inverted lists for any of the keywords, return an
  // empty list. 
  //
  // Optionally explore different (better) ways to sort the result list.
  Array<Pair<int, int>> process_query(String query)

// Main program:
//
// 1. Take a file name as first command line argument
// 2. Construct inverted index from given file
// 3. Read query from standard input
// 4. Process query and output the top-3 records (ordered by count); if less
//    than 3 hits, output less; if no hits, say that no hits
// 5. Optionally highlight query words
// 6. Repeat from 3
//
void main