First of all, here is the code. I changed the input type from List<String[]> to List<List<String>> as it does not really make sense to mix up both Lists and Arrays. This also applies to the output type.
The code
public static List<List<String>> merge(List<List<String>> dictionary) {
List<List<String>> newDictionary = new ArrayList<>();
for (List<String> stringPair : dictionary) {
List<Integer> matchIndices = new ArrayList<>();
for (int i = 0; i < newDictionary.size(); i++) {
List<String> newStrings = newDictionary.get(i);
for (String str : stringPair) {
if (newStrings.contains(str)) {
matchIndices.add(i);
}
}
}
if (matchIndices.size() == 0) {
newDictionary.addAll(new ArrayList<List<String>>(Collections.singleton(new ArrayList<>(stringPair))));
continue;
}
matchIndices.sort(Integer::compareTo);
if (matchIndices.size() == 1) {
newDictionary.get(matchIndices.get(0)).addAll(new ArrayList<>(stringPair));
} else {
int last = matchIndices.remove(0);
while (matchIndices.size() > 0) {
int i = matchIndices.get(0);
newDictionary.get(last).addAll(newDictionary.get(i));
newDictionary.remove(i);
matchIndices.remove(0);
matchIndices = new ArrayList<>(matchIndices.stream().map(a -> a - 1).toList());
}
}
}
newDictionary = newDictionary.stream()
.map(strings -> strings.stream().distinct().toList())
.toList();
return newDictionary;
}
How does it work?
dictionary the input of type List<List<String>> (inner List has max size of 2, even though the function would work with even more strings in theory)newDictionary the output of the function of type List<List<String>>
The following code is executed for every input pair/List of strings in directory
- Get all the existing different "groups" (their indicies) in
newDictionary in which the strings from the par are already present. This List of indices is called matchIndices
Example: stringPair=["A","E"] newDictionary:[["I", "A", "O"], ["P", "D"]] would result in matchIndices=[0] because only "A" is present one time in the first element of newDictionary
- If
matchIndices.size() is 0, create a new group in newDictionary with the string pair. Back to 1.
- If
matchIndices.size() is 1, append the strings from the pair to the specific newDictionary group with the index specified in matchIndices. Back to 1.
- If
matchIndices.size() is greater than 1, that means that multiple groups from newDictionary with the indices specified in matchIndices will have to be merged together in the for-loop. Back to 1.
In the end we have to make sure there are no duplicates in the Lists in newDictionary.
Main method
public static void main(String[] args) {
List<List<String>> dictionary = new ArrayList<>(List.of(
List.of("A", "B"),
List.of("B", "C"),
List.of("D", "E"),
List.of("F", "C"),
List.of("G", "H"),
List.of("T", "D")));
System.out.println(merge(dictionary));
}
Why do we need step 4?
In your specific example we don't have to merge multiple groups.
But with input data like this
List<List<String>> dictionary = new ArrayList<>(List.of(
List.of("A", "B"),
List.of("B", "C"),
List.of("D", "E"),
List.of("F", "E"),
List.of("E", "A")));
we eventually come to the point where newDictionary=[[A, B, B, C], [D, E, F, E]] and we have to try to insert [E, A]. Here both groups from newDictionary will have to be merged together.
This then results in the output of [[A, B, C, D, E, F]], where both groups are merged and removed duplicates.
P.s.
I am not really happy with this solution as it is not really clear what is actually going on, but I'm still posting this, because you said you would be happy with any solution. :)
