ArrayList of ArrayList of Integers should not accept duplicates

Question

The goal is to have no duplicates in my Arraylist of Arraylist of Integers "listResults". Here I iterate through a list of elements "listOfElements", and if the sum of two elements within this list is equal to the target, then I store indexes of both elements in an ArrayList "pair". Then I add that ArrayList to the list of ArrayList "listResults" and continue iterating. At the end I might end up with listResults containing one or more arrayLists. However I don't want it to contain duplicates like [2,3] and [3,2] or [4,0] and [0,4]

int target = 60;

ArrayList<ArrayList<Integer>> listResults = new ArrayList<ArrayList<Integer>>();
ArrayList<Integer> listOfElements = new ArrayList<Integer>();

listOfElements.add(1);
listOfElements.add(10);
listOfElements.add(25);
listOfElements.add(35);
listOfElements.add(60);

for (int i = 0; i < listOfElements.size(); i++) {
    for (int j = 0; j < listOfElements.size(); j++) {
        if (listOfElements.get(i) + listOfElements.get(j) == target) {
            ArrayList<Integer> pair = new ArrayList<Integer>();
            pair.add(i);
            pair.add(j);
            listResults.add(pair);
        }
    }
}

System.out.println(listResults);

Based on the current code, the output is: [ [2,3] , [3,2] ] but this is not acceptable as [2,3] and [3,2] are duplicates. Only [2,3] should be allowed as it was the first one to be added to the ArrayList.

Answer 1

You shouldn't check the already visited elements. In your inner for-loop,

change

int j = 0;

to

int j = i + 1;

Answer 2

如果条件为真，请使用break语句。