poj 2152 树形DP

思路：这个没思路，看了陈启峰的论文写得。

#include<map>

#include<set>

#include<cmath>

#include<queue>

#include<cstdio>

#include<vector>

#include<string>

#include<iomanip>

#include<cstdlib>

#include<cstring>

#include<iostream>

#include<algorithm>

#define pb push_back

#define mp make_pair

#define Maxn 1010

#define Maxm 80002

#define LL __int64

#define Abs(x) ((x)>0?(x):(-(x)))

#define lson(x) (x<<1)

#define rson(x) (x<<1|1)

#define clr(x,y) memset(x,y,sizeof(x))

#define inf 0x3f3f3f3f

#define lowbit(x) (x&(-x))

#define mod 1000000000

using namespace std;

int dp[Maxn][Maxn],best[Maxn],w[Maxn],d[Maxn],n,dis[Maxn],head[Maxn],vi[Maxn],e;

struct Edge{

    int u,v,next,val;

}edge[Maxn*2];

void init()

{

    clr(vi,0);

    clr(head,-1);

    e=0;

}

void add(int u,int v,int val)

{

    edge[e].u=u,edge[e].v=v,edge[e].val=val,edge[e].next=head[u],head[u]=e++;

    edge[e].u=v,edge[e].v=u,edge[e].val=val,edge[e].next=head[v],head[v]=e++;

}

void getdis(int u,int f)

{

    int i,v,sz;

    vi[u]=1;

    for(i=head[u];i!=-1;i=edge[i].next){

        v=edge[i].v;

        if(v==f) continue;

        dis[v]=dis[u]+edge[i].val;

        getdis(v,u);

    }

}

void dfs(int u,int f)

{

    int i,v,j;

    for(i=head[u];i!=-1;i=edge[i].next){

        v=edge[i].v;

        if(v==f) continue;

        dfs(v,u);

    }

    memset(dis,0,sizeof(dis));

    getdis(u,u);

    best[u]=inf;

    for(i=1;i<=n;i++){

        if(dis[i]>d[u]){dp[u][i]=inf;continue;}

        dp[u][i]=w[i];

        for(j=head[u];j!=-1;j=edge[j].next){

            v=edge[j].v;

            if(v==f) continue;

            dp[u][i]+=min(best[v],dp[v][i]-w[i]);

        }

        if(dp[u][i]<best[u])

            best[u]=dp[u][i];

    }

}

int main()

{

    int t,i,j,u,v,val;

    scanf("%d",&t);

    while(t--){

        init();

        scanf("%d",&n);

        for(i=1;i<=n;i++)

            scanf("%d",w+i);

        for(i=1;i<=n;i++)

            scanf("%d",d+i);

        for(i=1;i<n;i++){

            scanf("%d%d%d",&u,&v,&val);

            add(u,v,val);

        }

        dfs(1,0);

        printf("%d\n",best[1]);

    }

    return 0;

}