MemoryGame SoftUni

import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;

public class MemoryGame {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        List<String> sequence = Arrays.stream(scanner.nextLine().split(" ")).collect(Collectors.toList());
        String userInput = scanner.nextLine();
        int counter = 0;

        while (!userInput.equals("end")) {
            counter++;
            int[] userInputArray = Arrays.stream(userInput.split(" ")).mapToInt(Integer::parseInt).toArray();

            int firstIndex = userInputArray[0];
            int secondIndex = userInputArray[1];

            if (userIsCheating(firstIndex, secondIndex, sequence)) {
                System.out.println("Invalid input! Adding additional elements to the board");
                String penaltyNumber = String.format("-%da", counter);
                sequence.add(sequence.size()/2, penaltyNumber);
                sequence.add(sequence.size()/2, penaltyNumber);
                userInput = scanner.nextLine();
                //to ensure we have the next input before we move to the next While iteration (if that's the case
                // => the below userInput in line... will be skipped dute to the Continue statement
                continue;
                //if the user is cheating => we need to skip all the remaining operations
                // in this While iteration and "continue" to the next iteration of the While cycle
            }

            String firstNumber = sequence.get(firstIndex);
            String secondNumber = sequence.get(secondIndex);

            if (firstNumber.equals(secondNumber)) {
                sequence.remove(firstNumber);
                sequence.remove(secondNumber);
//the remove method recognizes that we pass an Object as firstNumber & secondNumber are Objects
//    Achieve the same by using indexes:
//                if (firstIndex < secondIndex) {
//                    sequence.remove(secondIndex);
//                    sequence.remove(firstIndex);
//                }
//                else {
//                    sequence.remove(firstIndex);
//                    sequence.remove(secondIndex);
//                }
                System.out.printf("Congrats! You have found matching elements - %s!%n", firstNumber);
            }
            else {
                System.out.println("Try again!");
            }

            if (sequence.size() == 0) {
                break;
            }

            userInput = scanner.nextLine();
        }

        if (sequence.isEmpty()) {
            System.out.printf("You have won in %d turns!", counter);
        }
        else {
            System.out.println("Sorry you lose :(");
            System.out.println(String.join(" ", sequence));
        }

    }

    private static boolean userIsCheating(int firstIndex, int secondIndex, List<String> sequence) {
        if (firstIndex == secondIndex) {
            return  true;
        }
        if (firstIndex <0 || firstIndex >= sequence.size()) {
            return  true;
        }
        if(secondIndex < 0 || secondIndex >= sequence.size()){
            return true;
        }

        return false;
    }
}