interview Q

Answer

import java.util.ArrayList;
import java.util.List;

public class DolevQ {
    public static void main(String[] args) {
        String s1 = "ilya";
        String s2 = "dolev";
        String s3 = "Engine";
        List<String> testList = new ArrayList<>();
        testList.add(s1);
        testList.add(s2);
        testList.add(s3);
        printAllComb(testList);
    }

    static void printAllComb(List<String> input) {
        int conters[] = new int[input.size()];
        do {
            StringBuffer stringBuffer = new StringBuffer();
            for (int i = 0; i < input.size(); i++) {
                String str = input.get(i);
                stringBuffer.append(str.charAt(conters[i]));
            }
            System.out.println(stringBuffer);

            int indexOfIncrement = getIndex(conters);
            if (conters[indexOfIncrement] + 1 < input.get(indexOfIncrement).length()) {
                conters[indexOfIncrement]++;
            } else {
                conters[indexOfIncrement] = 0;
                if (indexOfIncrement != 0) {
                    conters[indexOfIncrement - 1]++;
                }
            }
        }
        while (!isZeroCounters(conters));

    }

    private static int getIndex(int[] conters) {
        for (int i = 0; i < conters.length; i++) {
            if (conters[i] != 0) {
                return i;
            }
        }
        return conters.length - 1;
    }

    private static boolean isZeroCounters(int[] conters) {
        for (int c : conters) {
            if (c != 0) {
                return false;
            }
        }
        return true;
    }
}