高精度。。

// C = A + B, A >= 0, B >= 0
vector Add(vector& A, vector& B)
{
    if (A.size() < B.size()) return Add(B, A);
    vector C;
    int t = 0;
    for (int i = 0; i < A.size(); i ++ )
    {
        t += A[i];
        if (i < B.size()) t += B[i];
        C.push_back(t % 10);
        t /= 10;
    }
    if (t) C.push_back(1);
    return C;
}

// C = A - B, 满足A >= B, A >= 0, B >= 0
vector Sub(vector& A, vector& B)
{
    vector C;
    int t = 0;
    for (int i = 0; i < A.size(); i ++ )
    {
        t = A[i] - t;
        if (i < B.size()) t -= B[i];
        C.push_back((t + 10) % 10);
        t = t < 0 ? 1 : 0;
    }
    while (C.size() > 1 && C.back() == 0) C.pop_back();
    return C;
}

// C = A * b, A >= 0, b >= 0
vector Mul(vector& A, int b)
{
    vector C;
    int t = 0;
    for (int i = 0; i < A.size() || t; i ++ )
    {
        if (i < A.size()) t += A[i] * b;
        C.push_back(t % 10);
        t /= 10;
    }
    while (C.size() > 1 && C.back() == 0) C.pop_back();
    return C;
}

// C = A * B, A >= 0, B >= 0
vector Mul(vector& A, vector& B)
{
    vector C(A.size() + B.size());
    for (int i = 0; i < A.size(); i ++ )
    {
        for (int j = 0; j < B.size(); j ++ )
        {
            C[i + j] += A[i] * B[j];
        }
    }
    
    int t = 0;
    for (int i = 0; i < C.size(); i ++ )
    {
        t += C[i];
        C[i] = t % 10;
        t /= 10;
    }
    while (C.size() > 1 && C.back() == 0) C.pop_back();
    return C;
}

// A / b = C ... r, A >= 0, b > 0
vector Div(vector& A, int b, int& r)
{
    vector C;
    r = 0;
    for (int i = A.size() - 1; ~i; i -- )
    {
        r = r * 10 + A[i];
        C.push_back(r / b);
        r %= b;
    }
    reverse(C.begin(), C.end());
    while (C.size() > 1 && C.back() == 0) C.pop_back();
    return C;
}