nini.java

import java.util.ArrayList;
import java.util.Scanner;

public class Main {
    public static void main(String args[]) {
        Integer[] params = getParams();
        int size = params[0];
        int interval = params[1] + 1;
        int lastIndex = 0;
        ArrayList<Integer> children = createArrayList(size);

        while (children.size() >= 2) {
            int indexToDestroy = findNextIndexToRemove(interval, children.size() - 1, lastIndex);
            children.remove(indexToDestroy);
            lastIndex = indexToDestroy;
        }

        for (Integer value : children) {
            System.out.println("Value: " + value);
        }
    }

    /**
     * Find the next index to remove from the array
     *
     * @param interval to remove
     * @param limit the max limit allowed to restore the currentIndex
     * @param initIndex last position removed to start from it the next iteration
     * @return next index to remove
     */
    public static int findNextIndexToRemove(int interval, int limit, int initIndex) {
        int nextIndex = 0, counter = 1, currentIndex = initIndex;
        // I use while true because I don't know when to break it. So I will do it manually
        while (true) {
            if (currentIndex > limit) {
                currentIndex = 0;
            }

            nextIndex = currentIndex++;

            // If the round to iterate is the same at the interval,
            // break the loop
            if (counter == interval) break;

            counter++;
        }

        return nextIndex;
    }

    /**
     * Get array size and interval to calculate the final value
     *
     * @return Integer[]
     */
    public static Integer[] getParams() {
        Scanner reader = new Scanner(System.in);
        String input = null;
        int interval = -1, size = -1;
        do {
            System.out.print("Ingresar numero de ninos e intervalo de eliminacion => ");
            input = reader.nextLine();
            String[] values = input.split(" ");

            // Validate if the user enter a parseable value
            if (values.length == 2) {
                size = parseStringValue(values[0]);
                interval = parseStringValue(values[1]);
            }
        } while ((size < 1 || size > 1000) || (interval < 1 || interval > 100));

        return new Integer[]{size, interval};
    }

    /**
     * Create an initialize an array list with the provided size
     *
     * @param size create a arraylist of the given size
     * @return list with values
     */
    public static ArrayList<Integer> createArrayList(int size) {
        ArrayList<Integer> list = new ArrayList<>();
        for (int index = 1; index <= size; index++) {
            list.add(index);
        }
        return list;
    }

    /**
     * Check if a string is a valid number. Otherwise return -1 since
     * it is a invalid value
     *
     * @param value to parse, if it not a valid number, it will return -1, an invalid value for the system
     * @return a number
     */
    public static int parseStringValue(String value) {
        return isNumeric(value) ? Integer.parseInt(value) : -1;
    }

    /**
     * Check if a string is a number
     *
     * @param strNum number to validate
     * @return true if the number is valid, otherwise false
     */
    public static boolean isNumeric(String strNum) {
        if (strNum == null) {
            return false;
        }
        try {
            double d = Integer.parseInt(strNum);
        } catch (NumberFormatException nfe) {
            return false;
        }
        return true;
    }
}