793. 高精度乘法

 

 

#include <iostream>
#include <vector>
using namespace std;

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

int main()
{
    string a;
    int b;
    
    cin >> a >> b;
    vector<int> A;
    for (int i = a.size() - 1; i >= 0; -- i)    A.push_back(a[i] - '0');
    
    auto C = mul(A, b);
    
    for (int i = C.size() - 1; i >= 0; -- i)    cout << C[i];
    
    return 0;
}