MovieRecommend.java

package depth_first_search;

import java.util.*;

/**
 * Created by gouthamvidyapradhan on 25/02/2017.
 * Accepted
 */
public class MovieRecommend
{
    Set<Integer> visited = new HashSet<>();
    List<Movie> list = new ArrayList<>();
    class Movie
    {
        private int movieId;
        private float rating;
        private ArrayList<Movie> similarMovies;
        public List<Movie> getSimilarMovies()
        {
            return similarMovies;
        }
    }
    /**
     * Main method
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception
    {

    }

    public Set<Movie> getMovieRecommendations (Movie movie, int N)
    {
        dfs(movie);
        Set<Movie> result = new HashSet<>();
        Comparator<Movie> cmp = new Comparator<Movie>()
        {
            @Override
            public int compare(Movie o1, Movie o2)
            {
                return Float.compare(o2.rating, o1.rating);
            }
        };
        Collections.sort(list, cmp);

        if(list.size() < N)
        {
            result.addAll(list);
            return result;
        }

        for(int i = 0; i < N; i ++)
        {
            result.add(list.get(i));
        }

        return result;
    }

    private void dfs(Movie m)
    {
        visited.add(m.movieId); // mark this visited
        List<Movie> movies = m.getSimilarMovies();
        for(Movie mo : movies)
        {
            if(!visited.contains(mo.movieId))
            {
                list.add(mo);
                dfs(mo);
            }
        }
    }
}