Question

I do not have a smart or at least working idea how to solve following challenge:

I have 198 assignments and let each assignment solved by 10 persons, then I wrote everything in a PostgreSQL database by using Java hibernate & persistence API. That worked fine so far.

Sometimes I do have 10 different/distinct answers for an assignment – for other assignments I do have only 2 or 3 different/distinct answers (e.g. for the assignment “what is 5 + 5”, 8 persons told “10” and 2 persons told “25”)

Now I run a SQL statement to get a list with my assignments and the distinct answers:

 SELECT DISTINCT question, answer FROM survey INNER JOIN results ON results.survey_id=results.id;

what I get now is a result list that looks more or less like this:

+---------+----------+--------+
| ID      | Question | Answer | 
+---------+----------+--------+
| 1       | Q1      | 20      |
| 2       | Q1      | 22      | 
| 3       | Q1      | 25      | 
| 4       | Q1      | 21      | 
| 5       | Q1      | 22      | 
| 6       | Q1      | 10      | 
| 7       | Q1      | 20.5    |
| 8       | Q1      | 22.3    |
| 9       | Q1      | 28      |
| 10      | Q1      | 26      |
| 11      | Q2      | 52      |
| 12      | Q2      | 51      |
| 13      | Q3      | 78      |
| 14      | Q3      | 80      |
| ...     | ...     | ...     |
| ...     | ...     | ...     |
| ...     | ...     | ...     |
+---------+---------+---------+

now the challening part:

I want now randomly pick out 4 distinct answers (if possible) from each assignment (Q1, Q2, Q3, …) and create a new assignment where people have to vote on the best answer.

But as shown, sometimes I do have less then 4 distinct answers for an assignment. In this case I want to take everything that’s available.

How could I iterate through my list and perform this kind of “picking”?

P.S. it’s not very important to pick the answers randomly – would also be okay to pick the first 4 answers.

appreciate your help

regards

Answer 1

if the resultset is that small i would just

// if random is needed [see here][1] to adapt the criteria
var answers = session.createCriteria(Answer.class)
    .setFetchMode("Question", FetchMode.eager)
    .list<Answer>();


// map of orginal question to voting question
Map<Question, Question> questions = new Hashmap<Question, Question>();
for (Answer answer : answers)
{
    if (questions.ContainsKey(answer.getQuestion()))
    {
        Question votingQuestion = questions.get(answer.getQuestion());
        if (votingQuestion.getPossibleAnswers().Count() < 4)
            votingQuestion.getPossibleAnswers().add(answer.Text);
    }
    else
    {
        Question votingQuestion = createVotingQuestion(answer.getQuestion());
        votingQuestion.getPossibleAnswers().add(answer.Text);
        questions.add(answer.getQuestion(), votingQuestion);
    }
}