题解 | #【模板】高精度乘法#

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

const int N = 10005;

int a[N],b[N],c[N];
string s1,s2;

int main()
{
    cin>>s1>>s2;
    
    int la = s1.size(),lb = s2.size(),lc=la+lb;
    //vector<int>a(la,0),b(lb,0),c(lc,0);
    for(int i = 0;i<la;i++) a[i]=s1[la-i-1]-'0';
    for(int i = 0;i<lb;i++) b[i]=s2[lb-i-1]-'0';
    
    
    for(int i = 0;i<la;i++)
        for(int j = 0;j<lb;j++)
            c[i+j]+=a[i]*b[j];
    for(int i = 0;i<lc;i++)
    {
        c[i+1]+=c[i]/10;
        c[i]%=10;
    }
    while(c[lc-1]==0&&lc>1)lc--;
    for(int i = lc-1;i>=0;i--)
    {
        cout<<c[i];
    }
    cout<<endl;
    return 0;
}