public static List<Integer> intersectTwoPostingLists(List<Integer> l1, List<Integer> l2) {
List<Integer> intersection = PostingList.createList();
if (l1.isEmpty() || l2.isEmpty()) return intersection;
int idx1 = 0, idx2 = 0;
while (idx1 < l1.size() && idx2 < l2.size()) {
if (l1.get(idx1).equals(l2.get(idx2))) {
intersection.add(l1.get(idx1));
idx1++;
idx2++;
} else if (l1.get(idx1).compareTo(l2.get(idx2)) < 0) {
idx1++;
} else {
idx2++;
}
}
return intersection;
}
public RankedResults[] retrieveRankedDocuments(String query) {
String[] terms = getQueryTerms(query);
Map<Integer, Doc> documentList = obIndex.getDocsList();
double avgDocLen = obIndex.getAvgDocLength();
long collectionSize = obIndex.getTotalNoFiles();
Map<Integer, Double> weight1Map = new TreeMap<Integer, Double>();
Map<Integer, Double> weight2Map = new TreeMap<Integer, Double>();
for (String term : terms) {
PostingList postingList = obIndex.getPostingList(term);
if (postingList == null) {
System.out.println("Term: " + term + " doesn't exist in document collection");
continue;
}
int df = postingList.getNumberofDocs();
for (PostingListCell postingListCell : postingList.getDocsList()) {
Doc doc = documentList.get(postingListCell.getDocId());
int maxTf = doc.getMaxTermFrequency();
int docLen = doc.getTotalTerms();
int tf = postingListCell.getStemFreq();
double w1 =
(0.4 + 0.6 * Math.log(tf + 0.5) / Math.log(maxTf + 0.5))
* (Math.log(collectionSize / df) / Math.log(collectionSize));
double w2 =
0.4
+ 0.6
* (tf / (tf + 0.5 + 1.5 * docLen / avgDocLen))
* (Math.log(collectionSize / df) / Math.log(collectionSize));
int docId = doc.getDocumentId();
if (!weight1Map.containsKey(docId)) {
weight1Map.put(docId, 0.0);
}
weight1Map.put(docId, weight1Map.get(docId) + w1);
if (!weight2Map.containsKey(docId)) {
weight2Map.put(docId, 0.0);
}
weight2Map.put(docId, weight2Map.get(docId) + w2);
}
}
Comparator<Map.Entry<Integer, Double>> comparator =
new Comparator<Map.Entry<Integer, Double>>() {
public int compare(Map.Entry<Integer, Double> o1, Map.Entry<Integer, Double> o2) {
return o1.getValue().equals(o2.getValue())
? o1.getKey().compareTo(o2.getKey())
: o2.getValue().compareTo(o1.getValue());
}
};
List<Map.Entry<Integer, Double>> weight1List =
new ArrayList<Map.Entry<Integer, Double>>(weight1Map.entrySet());
List<Map.Entry<Integer, Double>> weight2List =
new ArrayList<Map.Entry<Integer, Double>>(weight2Map.entrySet());
Collections.sort(weight1List, comparator);
Collections.sort(weight2List, comparator);
RankedResults w1Results = new RankedResults();
RankedResults w2Results = new RankedResults();
for (int i = 0; i < 10; i++) {
if (weight1List.size() >= i) {
Doc docForW1 = documentList.get(weight1List.get(i).getKey());
w1Results.add(
new Result(
(i + 1),
weight1List.get(i).getValue(),
weight1List.get(i).getKey(),
docForW1.getDocumentName(),
docForW1.getDocumentTitle()));
}
if (weight2List.size() >= i) {
Doc docForW2 = documentList.get(weight2List.get(i).getKey());
w2Results.add(
new Result(
(i + 1),
weight2List.get(i).getValue(),
weight2List.get(i).getKey(),
docForW2.getDocumentName(),
docForW2.getDocumentTitle()));
}
}
return new RankedResults[] {w1Results, w2Results};
}