Solved case5: //Write your code here HashSet pairs = new HashSet<>();

for (int i = 0; i < t; i++) {
    // Create unique pair representation
    String pair = pair_left[i] + " " + pair_right[i];
    // Add to HashSet (automatically handles duplicates)

    // Print current size after each addition
    String inverse_pair  =  pair_right[i] + " " + pair_left[i];
        if(!pairs.contains(inverse_pair)) 
        pairs.add(pair);
        System.out.println(pairs.size());
}