高精度乘法

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() == 0) C.pop_back();

return C;
}