[LOJ2538][PKUWC2018]Slay the Spire(DP)

https://blog.csdn.net/maxwei_wzj/article/details/80789619

感觉主要难在想到通过f,g来求F,G。

代码实现调换了题解中f,g的两维。

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define rep(i,l,r) for (int i=(l); i<=(r); i++)
typedef long long ll;
using namespace std;

const int N=3010,mod=998244353;
int T,n,m,k,ans,C[N][N],wg[N],wf[N],g[N][N],f[N][N],sg[N][N],sf[N][N];

bool cmp(int a,int b){ return a>b; }

int G(int x,int y){
    if (x>n || x<y) return 0;
    if (!y) return C[n][x];
    int res=0;
    rep(i,1,n) res=(res+1ll*g[y][i]*C[n-i][x-y])%mod;
    return res;
}

int F(int x,int y){
    if (x>n || x<y) return 0;
    int res=0;
    rep(i,1,n) res=(res+1ll*f[y][i]*C[n-i][x-y])%mod;
    return res;
}

int main(){
    freopen("slay.in","r",stdin);
    freopen("slay.out","w",stdout);
    for (scanf("%d",&T); T--; ){
        scanf("%d%d%d",&n,&m,&k); ans=0; C[0][0]=1;
        rep(i,1,n){ C[i][0]=1; rep(j,1,i) C[i][j]=(C[i-1][j]+C[i-1][j-1])%mod; }
        rep(i,1,n) scanf("%d",&wg[i]);
        rep(i,1,n) scanf("%d",&wf[i]);
        sort(wg+1,wg+n+1,cmp); sort(wf+1,wf+n+1,cmp);
        rep(i,0,n) rep(j,0,n) f[i][j]=g[i][j]=sf[i][j]=sg[i][j]=0;
        rep(i,0,n) g[0][i]=sg[0][i]=1;
        rep(i,1,k) rep(j,i,n)
            g[i][j]=1ll*wg[j]*sg[i-1][j-1]%mod,sg[i][j]=(sg[i][j-1]+g[i][j])%mod;
        rep(i,1,k) rep(j,i,n)
            f[i][j]=(1ll*wf[j]*C[j-1][i-1]%mod+sf[i-1][j-1])%mod,sf[i][j]=(sf[i][j-1]+f[i][j])%mod;
        rep(i,0,k-1) ans=(ans+1ll*G(i,i)*F(m-i,k-i))%mod;
        rep(i,k,m-1) ans=(ans+1ll*G(i,k-1)*F(m-i,1))%mod;
        printf("%d
",ans);
    }
    return 0;
}