epr24pr1_ojanssen2/main.cpp

#include "std_lib_inc.h"

constexpr vector<string> first_digit_strings = {
"", "ein", "zwei", "drei", "vier", "fuenf", "sechs", "sieben", "acht", "neun"
};

constexpr vector<string> middle_digit_strings = {
"", "zehn", "zwanzig", "dreissig", "vierzig", "fuenfzig", "sechzig", "siebzig", "achzig", "neunzig"
};

int main()
{
    int input;
    /*
     * Use while (true) with break instead of while(cin) to be able to instantly stop the loop in case of an invalid input
     */
    while (true)
    {
        cin >> input;
        if (!cin)
            break; // Stop running loop, if input is wrong
        if (input < 1 || input > 999)
        {
            cout << "Zahl ausserhalb des gueltigen Bereichs.\n";
            continue;
        }

        const int right_digit = input % 10;
        const int middle_and_right_digit = input % 100;
        const int middle_digit = ((middle_and_right_digit) - right_digit) / 10;

        vector<string> result;
        string number_constructor = "";
        if (middle_and_right_digit < 11 || middle_and_right_digit > 12)
        {
            // Handle everything else
            if (right_digit == 1)
                number_constructor = "s";
            if (middle_digit > 1 && right_digit != 0)
                number_constructor = "und";
            number_constructor = first_digit_strings[right_digit] + number_constructor;
        }
        else
        {
            // Handle 11 and 12
            if (middle_and_right_digit == 11)
                number_constructor = "elf";
            else
                number_constructor = "zwoelf";
        }
        result.push_back(number_constructor);

        if ((input > 9 /*input_length > 1*/) && (middle_and_right_digit < 11 || middle_and_right_digit > 12))
            result.push_back(middle_digit_strings[middle_digit]);
        else
            result.push_back("");

        if (input > 99 /*input_length >= 3*/)
        {
            int left_digit = ((input % 1000) - middle_digit) / 100;
            if (left_digit != 1)
                number_constructor = first_digit_strings[left_digit];
            else
                number_constructor = "";
            result.push_back(number_constructor + "hundert");
        }
        else
            result.push_back("");

        cout << result[2] << result[0] << result[1] << "\n";
    }
    cout << "Eingabe beendet.\n";
    return 0;
}