输入

string a;
cin >> a;
vector<int> A;
for (int i = a.length() - 1; i >= 0; i--)
{
    A.push_back(a[i] - '0');
}

输出

for (int i = A.size() - 1; i >= 0; i--)
{
    cout << A[i];
}

高精度加法
A>=0,B>=0

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

高精度减法
A>=B,A>=0,B>=0

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

高精度乘法
高精度乘低精度 A>=0,b>=0

vector<int> mul(vector<int> A, int b)
{
    vector<int> 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())
    {
        C.pop_back();
    }
    return C;
}

高精度除法
A>=0,b>0

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