C++ 解法, 执行用时: 194ms, 内存消耗: 1296K, 提交时间: 2023-08-12 10:20:01

#include<iostream>
#include<string>
#include<algorithm>
#include<queue>
using namespace std;
#define ll long long
const int N=300005;
const ll mod=998244353;
ll qpow(ll a,ll b){
	ll ans=1;
	if(b==0)
	return 1;
	if(b%2)
	ans=a;
	ll t=qpow(a,b/2);
	return t*t%mod*ans%mod;
}
ll inv(ll a){
	return qpow(a,mod-2);
}
void solve(){
	ll n,p;
    cin>>n>>p;
    ll q=(mod+1-p)%mod;
    ll s=p*inv(q)%mod;
    s=inv(s);
    if(s==1){
        cout<<inv(2)<<'\n';
        return;
    }
    ll ans=n*qpow(s,n)%mod*(s-1)%mod*inv(qpow(s,n+1)-1)%mod*inv(qpow(s,n)-1)%mod;
    ll ans2=inv(qpow(s,n+1)-1)%mod;
    ans=(ans-ans2+mod)%mod;
    cout<<ans;
    cout<<'\n';
}
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	int t0;
	cin>>t0;
	for(int t=0;t<t0;t++){
		solve();
	}
}