3836: [Poi2014]Tourism

樹形dp，多開一維記錄祖先狀態；
轉移時其實是使用的泛化揹包的轉移方式，使程序簡潔高效；

#include<bits/stdc++.h>
#define rep(i,k,n) for(int i=k;i<=(n);i++)
using namespace std;
const int N=20005;
const int M=100005;
const int inf=0x3f3f3f3f;
struct E{
    int to,next;E(int to=0,int next=0):to(to),next(next){}
}edge[M];
int head[N],tot=0,C[N],bin[13];
inline void mi(int &x,int y){
    if(y<x)x=y;
}
void add(int x,int y){
    edge[++tot]=E(y,head[x]);head[x]=tot;
    edge[++tot]=E(x,head[y]);head[y]=tot;
}
int n,m,vis[N],f[12][60000],dep[N],stk[N],top;
void dfs(int x){int d;
    vis[x]=1;
    int s=bin[dep[x]+1];
    if(!(d=dep[x]))f[0][0]=C[x],f[0][1]=0,f[0][2]=inf;
    else {
    rep(i,0,s-1)f[d][i]=inf;
    top=0;
    for(int i=head[x];i;i=edge[i].next){
        int v=edge[i].to;
        if(vis[v]&&dep[v]<dep[x])stk[++top]=dep[v];
    }
        rep(i,0,bin[d]-1){
            int ne=i,t=1;
            rep(j,1,top){
                int v=stk[j];
                int op=(i/bin[v])%3;
                if(op==1)ne=ne+bin[v];
                else if(!op)t=2;
            }
            mi(f[d][i+t*bin[d]],f[d-1][i]);
            mi(f[d][ne],f[d-1][i]+C[x]);
        }
    }
    for(int i=head[x];i;i=edge[i].next){
        int v=edge[i].to;
        if(!vis[v]){
            dep[v]=dep[x]+1,dfs(v);
            rep(i,0,s-1)
            f[d][i]=min(f[d+1][i],f[d+1][i+2*bin[d+1]]);
        }
    }
}
int main(){
//  freopen("in.in","r",stdin);
    bin[0]=1;rep(i,1,12)bin[i]=bin[i-1]*3;
    scanf("%d%d",&n,&m);
    rep(i,1,n)scanf("%d",&C[i]);
    int x,y;
    rep(i,1,m){
        scanf("%d%d",&x,&y);
        add(x,y);
    }int ans=0;
    rep(i,1,n){
        if(!vis[i]){
        dfs(i);
        ans+=min(f[0][0],f[0][2]);
       }
    }
    printf("%d\n",ans);
}