LinkedListMultimap or MultiMap sequence

Question

I have the following multiMap:

1st: [3=>[4,5]]
2nd: [2=>[3]]
3rd: [0=>[2]]
4th: [5=>[1]]
5th: [4=>[1]]

I would like to get the sequence out of it such as:

0->2->3->[4,5]->1

Is it possible?

This is what I have tried, but doesn't seem to work correctly:

// the starting point is given from the start.

Collection<String> col = new HashSet<String>();
col.add("0");
buildPath2(myMultimap, col, result2);

static void buildPath2(Multimap<String, String> path, Collection<String> token, List<Collection<String>> result2) {
    if (token != null) {
        result2.add(token);
        Collection<String> c = null;
        for (String elem: token){
           c = path.get(elem);
        }
        buildPath2(path, c, result2);
    }
}

my question is to how to get this sequence 0->2->3->[4,5]->1? — Zuser, Jan 14 '15 at 09:40
It is not always possible if you want to start with `0`. Indeed, you could have some association like `5=>[3,0,2]`. — , Jan 14 '15 at 09:51
This is missing in the problem statement. And if your multimap contains `5=>[3,0,2]`, your algorithm can fail to find the cycle when it starts with `0`. — , Jan 14 '15 at 10:00

score 0 · Answer 1 · 2015-01-14T09:59:12.513

0

Choose the starting index
Assign starting index to current index
do
  output path[current index]
  current index= path[current index][some index°]
while current index != starting index

°Depending on your exact policy. Will normally be the last index in the list.

edited Jan 14 '15 at 09:59

answered Jan 14 '15 at 09:48

score 0 · Accepted Answer · answered Jan 14 '15 at 11:06

You've got two basic problems that you'll need to resolve.

Your program doesn't seem to output anything. Somewhere in there, you'll want to output result2 somehow.
After your for loop, c will be whatever you get from looking up the last element of token in the map. You probably wanted it to be a Set containing what you get from looking up all the elements of token in the map.

To deal with issue 2, you should probably change

Collection<String> c = null;
for (String elem: token){
   c = path.get(elem);
}

to

Collection<String> c = new HashSet<>();
for (String elem : token) {
    c.addAll(path.get(elem));
}

LinkedListMultimap or MultiMap sequence

2 Answers2