InvertedIndex.java

import java.util.*;
import java.io.*;
public class InvertedIndex {
	String[] myDocs;
	ArrayList<String> termList;
	ArrayList<ArrayList<Integer>> docLists;
	
	public InvertedIndex(String[] docs){
		myDocs = docs;
		termList = new ArrayList<String>();
		docLists = new ArrayList<ArrayList<Integer>>();
		ArrayList<Integer> docList;
		for(int i=0;i<myDocs.length;i++){
			String[] tokens = myDocs[i].split(" ");
			for(String token:tokens){
				if(!termList.contains(token)){//a new term
					termList.add(token);
					docList = new ArrayList<Integer>();
					docList.add(new Integer(i));
					docLists.add(docList);
				}
				else{//an existing term
					int index = termList.indexOf(token);
					docList = docLists.get(index);
					if(!docList.contains(new Integer(i))){
						docList.add(new Integer(i));
						docLists.set(index, docList);
					}
				}
			}
		}
	}
	
	public String toString(){
		String matrixString = new String();
		ArrayList<Integer> docList;
		for(int i=0;i<termList.size();i++){
			matrixString += String.format("%-15s", termList.get(i));
			docList = docLists.get(i);
			for(int j=0;j<docList.size();j++)
				matrixString += docList.get(j) + "\t";
			matrixString += "\n";
		}
		return matrixString;
	}
	/* public int getLenth(String strn){
	    	int len =0;
	    	ArrayList<Integer> docList;
			for(int i=0;i<termList.size();i++){
				if(strn==termList.get(i).toString()){
				docList = docLists.get(i);
				len=docList.size();}
				//for(int j=0;j<docList.size();j++)
					//System.out.printf(" "+docList.get(j));
		    	//System.out.println(docList.size());
				}
	    	return len;
	    }*/
	public ArrayList<Integer> search(String query){
		int index = termList.indexOf(query);
		if(index <0)
			return null;
		return docLists.get(index);
	}
	
	public ArrayList<Integer> search(String[] query){
		ArrayList<Integer> result = search(query[0]);
		int termId = 1;
		while(termId<query.length){
			//System.out.println(query[termId]);
			ArrayList<Integer> result1 = search(query[termId]);
			result = merge(result, result1);
			termId++;
		}
		return result;
	}
	
	private ArrayList<Integer> merge(ArrayList<Integer> l1, ArrayList<Integer> l2){
		ArrayList<Integer> mergedList = new ArrayList<Integer>();
		int id1=0, id2=0;
		while(id1<l1.size()&&id2<l2.size()){
			if(l1.get(id1).intValue()==l2.get(id2).intValue()){
				mergedList.add(l1.get(id1));
				id1++;
				id2++;
			}
			else if(l1.get(id1)<l2.get(id2))
				id1++;
			else
				id2++;
		}
		return mergedList;
	}
	
	public static void main(String[] args){
		String[] docs = {"new home sales top forecasts",
					     "home sales rise in july",
					     "increase in home sales in july",
					     "july new home sales rise"
		};
		InvertedIndex inverted = new InvertedIndex(docs);
		System.out.println(inverted);
		ArrayList<Integer> result = inverted.search(args);
		if(result!=null){
			for(Integer i:result)
				System.out.println(docs[i.intValue()]);
		}
		else
			System.out.println("No match!");
	}
}