4.5

import java.util.Scanner;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

public class Main {
    private static int[] sequence;
    private static int[] answers;
    private static final int MAX_PEOPLE_VALUE = 10000;
    private static final int MIN_PEOPLE_VALUE = 1;

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        int numOfElements = 0;

        System.out.println("This program finds palindrome in a sequence of numbers.");
        int inputMethodChoice = chooseInputMethod(scanner);

        answers = new int[2];

        if (inputMethodChoice == 1) {
            numOfElements = setNumOfElements(scanner, MIN_PEOPLE_VALUE, MAX_PEOPLE_VALUE);
            sequence = new int[numOfElements];
            inputDataManually(scanner, numOfElements);
        } else if (inputMethodChoice == 2) {
            String filePath = findFile(scanner);
            numOfElements = inputDataFromFile(filePath);
        }

        findPalindrome(numOfElements);
        outputAnswer(answers[0], answers[1]);
        writeToFile(scanner, answers[0], answers[1]);

        scanner.close();

    }

    private static void outputAnswer(int i, int j) {
        if (i != j) {
            System.out.println("I = [" + (i + 1) + "], J = ["+ (j + 1) + "] - indexes of palindrome.");
        }
        else {
            System.out.println("This array of numbers does not have a palindrome");
        }

//        outputInFile(i, j);
    }
    private static int chooseInputMethod(Scanner scanner) {
        int choice;
        do {
            System.out.println("Choose an option:");
            System.out.println("1. Input sequence manually");
            System.out.println("2. Read sequence from a text file");

            while (!scanner.hasNextInt()) {
                System.out.println("Invalid input. Please enter 1 or 2.");
                scanner.next();
            }
            choice = scanner.nextInt();
            scanner.nextLine();
            if (choice != 1 && choice != 2) {
                System.out.println("Error! You have to input either 1 or 2.");
            }
        } while (choice != 1 && choice != 2);
        return choice;
    }

    private static int setNumOfElements(Scanner scanner, int min, int max) {
        int numOfElements;
        do {
            System.out.println("Enter the number of elements in sequence:");
            while (!scanner.hasNextInt()) {
                System.out.println("Invalid input. Please enter a valid integer.");
                scanner.next();
            }
            numOfElements = scanner.nextInt();
            scanner.nextLine();
            if (numOfElements < min || numOfElements > max) {
                System.out.println("Please enter a value from " + min + " to " + max + "!");
            }
        } while (numOfElements < min || numOfElements > max);
        return numOfElements;
    }

    private static void inputDataManually(Scanner scanner, int numOfElements) {
        for (int i = 0; i < numOfElements; i++) {
            System.out.println("Enter element number " + (i + 1) + " : ");
            int elementValue = scanner.nextInt();
            sequence[i] = elementValue;
        }
    }
    private static boolean isPalindrome(int left, int right) {
        boolean isCorrect;

        if (left >= right) {
            isCorrect = true;
        }
        else {
            isCorrect = ((sequence[left] == sequence[right]) && isPalindrome(left + 1, right - 1));
        }

        return isCorrect;
    }

    private static void findPalindrome(int size) {
        int indexI, indexJ;
        int maxI, maxJ;

        maxI = 0;
        maxJ = 0;
        for (indexI = 0; indexI < size; indexI++) {
            for (indexJ = size - 1; indexJ > indexI; indexJ--) {
                if (isPalindrome(indexI, indexJ)) {
                    if ((indexJ - indexI) > (maxJ - maxI)) {
                        maxI = indexI;
                        maxJ = indexJ;
                    }
                }
            }
        }
        answers[0] = maxI;
        answers[1] = maxJ;
    }

    private static String findFile(Scanner scanner) {
        String filePath;
        boolean isCorrect;
        do {
            isCorrect = true;
            System.out.print("Enter path to the file: ");
            filePath = scanner.nextLine();
            File file = new File(filePath);
            if (!file.exists()) {
                isCorrect = false;
                System.out.println("File not found at the specified path.");
            } else if (!filePath.endsWith(".txt")) {
                isCorrect = false;
                System.out.println("Error, wrong file type! File should have .txt extension.");
            }
        } while (!isCorrect);
        System.out.println("File found.");
        return filePath;
    }
    private static int inputDataFromFile(String path) {
        int numOfElements = 0;
        try (Scanner fileScanner = new Scanner(new File(path))) {
            System.out.println("Reading file...");

            String line = fileScanner.nextLine();
            String[] parts = line.split(" ");

            numOfElements = Integer.parseInt(parts[0]);
            sequence = new int[numOfElements];

            line = fileScanner.nextLine();
            parts = line.split(" ");

            for (int i = 0; i < numOfElements; i++) {
                sequence[i] = Integer.parseInt(parts[i]);
            }
        } catch (IOException e) {
            System.out.println("Error reading file!");
        }
        return numOfElements;
    }
    private static void writeToFile(Scanner scanner, int i, int j) {
        try {
            System.out.print("Enter file name: ");
            String fileName = scanner.nextLine();
            fileName += ".txt";
            FileWriter writer = new FileWriter(fileName);

            if (i != j) {
                writer.write("I = [" + (i + 1) + "], J = ["+ (j + 1) + "] - indexes of palindrome.");
            }
            else {
                writer.write("This array of numbers does not have a palindrome");
            }

            writer.close();

            System.out.println("Results written to " + fileName);
        } catch (IOException e) {
            System.out.println("Error writing to file!");
        }
    }
}