793. 高精度乘法

思路：
t表示进位

代码：

# include<iostream>
# include<cstring>
# include<cstdio>
# include<algorithm>
# 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() || 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;
}

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--) printf("%d",c[i]);
    
    return 0;
}