C++ :

#include <iostream>
#include <algorithm>

using namespace std;

const int N = 1010;

struct Node
{
    int father, size, sum;
    double avg;
}nodes[N];

int n, root;

int find() //找权值最大的根节点
{
    double avg = 0;
    int res = -1;
    for(int i = 1; i <=n; i++)
        if(i != root && avg < nodes[i].avg)
        {
            avg = nodes[i].avg;
            res = i;
        }
    return res;    
}

int main()
{
    int res = 0;
    cin >> n >> root;
    for(int i = 1; i <= n; i++)
    {
        auto &nd = nodes[i];
        cin >> nd.sum;
        nd.size = 1;
        nd.avg = nd.sum;
        res += nd.sum; //初始赋值 每个数乘一加一块，所有数的和
    }
    for(int i = 0, a, b; i < n - 1;i++)
    {
        cin >> a >> b;
        nodes[b].father = a;
    }
    
    for(int i = 0; i < n - 1; i++)
    {
        int ver = find();
        int f = nodes[ver].father;
        res += nodes[ver].sum * nodes[f].size;
        nodes[ver].avg = -1;
        for(int j = 1; j <= n; j++)
            if(nodes[j].father == ver)
                nodes[j].father = f;
        nodes[f].sum += nodes[ver].sum;
        nodes[f].size += nodes[ver].size;
        nodes[f].avg = (double)nodes[f].sum / nodes[f].size;
    }
    cout << res << endl;
    return 0;
}