高精度乘法模板

• 高精度乘高精度

vector<int> mul(vector<int> &A, vector<int> &B) {
    vector<int> C(A.size() + B.size(), 0); 
    for (int i = 0; i < A.size(); i++)
        for (int j = 0; j < B.size(); j++)
            C[i + j] += A[i] * B[j];
    for (int i = 0, t = 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;
}