C++ :

#include<iostream>
#include<algorithm>
#include<cstdio>
using namespace std;
int n;
bool b[6001];
int a[6001];
int ne;//总结点 
int f[6001][2];//寻根 
int hd[6001];
struct jiegouti{
	int v;
	int next;
};
struct jiegouti e[6001];
void so(int v,int u)
{
	ne++;
	e[ne].v=v;
	e[ne].next=hd[u];
	hd[u]=ne;
}
void dp(int u)
{
	f[u][1]=a[u];//1是要，0是不要 
	f[u][0]=0;
	for(int i=hd[u];i!=0;i=e[i].next)
	{
		int v=e[i].v;
		dp(v);
		f[u][1]+=f[v][0];
		f[u][0]=f[u][0]+max(f[v][1],f[v][0]);
	} 
	
}
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
	cin>>a[i];
	int l,k;
	while(cin>>l>>k&&l!=0&&k!=0)
	{
		b[l]=1;
		so(l,k);
	}
	for(int i=1;i<=n;i++)
	{
		if(b[i]==0)
		{
			dp(i);
			cout<<max(f[i][0],f[i][1]);
			break;
		}
	}
	return 0;
}

Pascal :

program dinner;
type link=^node;
     node=record
          s:longint;
          next:link;
     end;
var r:array[1..6000]of longint;
    sum:array[1..6000,0..1]of longint;
    son:array[1..6000]of link;
    n,root:longint;
function maxnum(a,b:longint):longint;
begin
  if a>b then maxnum:=a
  else maxnum:=b;
end;{maxnum}
procedure init;
var a,b,i:longint;
    p:link;
begin
  readln(n);
  for i:=1 to n do
    begin
      readln(r[i]);
    end;{for-i}
  readln(a,b);
  while (a<>0)and(b<>0) do
    begin
      inc(root,a);
      new(p);
      p^.s:=a;
      p^.next:=son[b];
      son[b]:=p;
      readln(a,b);
    end;{while}
  root:=(n*(n+1)div 2)-root;
end;{init}
procedure calc(k:longint);
var p:link;
    i:longint;
begin
  sum[k,0]:=0;
  sum[k,1]:=0;
  p:=son[k];
  while p<>nil do
    begin
      i:=p^.s;
      calc(i);
      inc(sum[k,0],maxnum(sum[i,0],sum[i,1]));
      inc(sum[k,1],sum[i,0]);
      p:=p^.next;
    end;{while}
  inc(sum[k,1],r[k]);
end;{calc}
procedure output;
begin
  writeln(maxnum(sum[root,0],sum[root,1]));
end;{out}
begin{main}
  init;
  calc(root);
  output;
end.