For simplicity, let’s say I have an ArrayList
whose indices contain exactly one single-digit integer. For instance:
JavaScript
x
6 4 5 6 0 6 3 4 1 6 1 6 0 6 8 3
I would like to filter out all occurrences of the sublist 6 0 6
, such that the new list becomes:
JavaScript
6 4 5 3 4 1 6 1 8 3
Is there any way of doing this? Using ListIterator
doesn’t seem to work for me, because I have to consider three consecutive elements collectively and I’m honestly not sure how to do that.
Here’s a skeleton of the method I have implemented:
JavaScript
public static void filterList(ArrayList<Integer> list) {
ListIterator<Integer> iterator = list.listIterator();
int elem;
while (iterator.hasNext()) {
// Remove any sublist of 6 0 6
}
}
Edit: Again, for simplicity, let’s assume there won’t be cases where we have 60606 or similar.
Advertisement
Answer
You can create an efficient and concise O(nm) solution by using Collections.indexOfSubList
:
JavaScript
public static void removeAllSubList(List<?> list, List<?> subList) {
// find first occurrence of the subList in the list, O(nm)
int i = Collections.indexOfSubList(list, subList);
// if found
if (i != -1) {
// bulk remove, O(m)
list.subList(i, i + subList.size()).clear();
// recurse with the rest of the list
removeAllSubList(list.subList(i, list.size()), subList);
}
}