2. Numeral System

#include <iostream>
#include <string>
#include <vector>

void readInput(std::string& numeralSystemStr, std::string& numberOne, std::string& numberTwo) {
    std::cin >> numeralSystemStr >> numberOne >> numberTwo;
}

std::vector<char> createNumeralSystem(const std::string& numeralSystemStr) {
    std::vector<char> vec;
    for (const char letter : numeralSystemStr) {
        vec.push_back(letter);
    }
    return vec;
}

int createIntFromDigits(const int& digit, int& number) {
    if (digit == 0) {
        number *= 10;
    } else {
        number *= 10;
        number += digit;
    }
    return number;
}

int convertStrToInt(std::vector<char> numeralSystem, const std::string& strNumber) {
    int number = 0;
    size_t size = numeralSystem.size();
    for (const char letter : strNumber) {
        for (size_t i = 0; i < size; ++i) {
            if (letter == numeralSystem[i]) {
                number = createIntFromDigits(i, number);
                break;
            }
        }
    }
    return number;
}

std::string convertIntToStr(const std::vector<char>& numeralSystem, const int& sum) {
    std::string sumToString = std::to_string(sum);
    std::string finalStr;
    for (const char letter : sumToString) {
        int i = int(letter) - '0';
        finalStr.push_back(numeralSystem[i]);
    }
    return finalStr;
}

void printResult(const std::string& stringSum) {
    std::cout << stringSum;
}

int main()
{
    std::string numeralSystemStr;
    std::string numberOne;
    std::string numberTwo;
    readInput(numeralSystemStr, numberOne, numberTwo);
    std::vector<char> numeralSystem = createNumeralSystem(numeralSystemStr);
    int numberOneInt = convertStrToInt(numeralSystem, numberOne);
    int numberTwoInt = convertStrToInt(numeralSystem, numberTwo);
    int intSum = numberOneInt + numberTwoInt;
    std::string stringSum = convertIntToStr(numeralSystem, intSum);
    printResult(stringSum);
}