题解 | 丛林木马

#include <bits/stdc++.h>
using namespace std;
const int N=2e6+10;
const int mod = 998244353;
typedef long long ll;
typedef unsigned long long ull;
const ll INF = 1e18;
ll n,m;
ll fac[N];
string num1;
string num2;
ll sz1,sz2;
void solve()
{   
    cin>>num1>>num2;
    sz1 = num1.size();
    sz2 = num2.size();
    num1 = " "+num1;
    num2 = " "+num2;

    ll res =  0;
    for(int i=1;i<=sz1;i++)
    {
        ll cur = num1[i]-'0';
        res = (res+cur*fac[sz1-i]%mod*sz2%mod)%mod;

    }


    for(int i=1;i<=sz2;i++)
    {
        ll cur = num2[i]-'0';
        res = (res+cur*fac[sz2-i]%mod*sz1%mod)%mod;

    }

    cout<<res<<'\n';

    

}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    fac[0]=1;
    for(int i=1;i<=N-10;i++)
    {
        fac[i]=fac[i-1]*10%mod;
    }
    int t=1;
    cin>>t;
    while(t--)
    {
        solve();

    }


    return 0;
}