Hdu2196（樹形dp，只有代碼)

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int num=6*1e3+10;
struct node
{
    int v,next;
}e[num];
int head[num],p[num],cnt;
int a[num];
int dp[num][2];
void int_i(void)
{
    memset(dp,0,sizeof(dp));
    memset(head,0,sizeof(head));
    memset(p,0,sizeof(p));
    cnt=0;
    return ;
}
void addedge(int u,int v)
{
    e[++cnt].v=v;
    e[cnt].next=head[u];
    head[u]=cnt;
    p[v]++;
    return ;
}
void dfs(int u,int f)
{
    dp[u][1]=a[u];
    dp[u][0]=0;
    for(int i=head[u];i;i=e[i].next)
    {
        int v=e[i].v;
        if(v==f) continue;
     
        dfs(v,u);
        dp[u][1]=max(dp[u][1],dp[u][1]+dp[v][0]);
        dp[u][0]=max(dp[u][0],dp[u][0]+max(dp[v][1],dp[v][0]));
    }
    return;
}
int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        int_i();
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&a[i]);
        }

        int u,v;//v is boss;
        while(scanf("%d%d",&u,&v)&&(u||v))
        {
            addedge(v,u);
        }

        for(int i=1;i<=n;i++)
        {
            if(p[i]==0)
            {
                dfs(i,-1);
                //pay attention on that dp maybe is less 0;
                printf("%d\n",max(dp[i][0],dp[i][1]));
                break;
            }
        }
    }
    return 0;
}