Bai2_Hash_FoldShift_Accepted

int foldShift(long long key, int addressSize)
{
    string str = to_string(key);
    int ret = 0;
    for (unsigned int i = 0; i < str.length(); i+= addressSize)
        ret += stoi(str.substr(i, addressSize));
    int x = pow(10, addressSize);
    return ret % x;
}

int rotation(long long key, int addressSize)
{
    string str = to_string(key);
    char last = str.back();
    str.pop_back();
    str = last + str;
    return foldShift(stoll(str), addressSize);
}