I题 具体看代码里的注释 #include<bits/stdc++.h> using namespace std; const int N=5005,mod=998244353; typedef long long LL; const double eps=1e-7; LL a[N],inv[N]; LL n; LL qsm(LL a,LL n){ LL res=1; while(n){ if(n&1)res=(LL)res*a%mod; a=(LL)a*a%mod; n>>=1; } return res; } LL f[N][N]; int main(){ ...