#include #include using namespace std; typedef long long ll; typedef pair pll; const ll MOD=998244353; int non_neg_mod(ll x){ return (x%MOD+MOD)%MOD; } int main(){ ios::sync_with_stdio(false); cin.tie(nullptr); //这个dp倒是很简单,dp[len][-2][-1] //dp[len+1][j][r]=sigma(i=1 to j-1)dp[len][i][j]/sigma(i=j+1 to k)dp[len][i][j] //可以预处理sigma(i=1 to j-1)dp[len][i][j],O(k^2) int n,k; cin>>n>>k; vector>> dp(n+1); vector pre(k+1); vector suf(k+1); for(int i=2;i<=n;i++){ dp[i].resize(k+1); if(i==2){ for(int j=0;j