1338：【例3-3】医院设置

#include <bits/stdc++.h>
using namespace std;

struct Node {
    int value; // 值
    int left; // 左子
    int right; // 右子
    int dad; // 父亲
    int level; // 层级
};

void ShowTree(const vector<Node> &a)
{
    cout << "value, left, right, data, level" << endl;
    for (int i = 1; i < a.size(); i++) {
        cout << a[i].value << " ";
        cout << a[i].left << " ";
        cout << a[i].right << " ";
        cout << a[i].dad << " ";
        cout << a[i].level << endl;
    }
}

int FindRoot(const vector<Node> &a)
{
    for (int i = 1; i < a.size(); i++) {
        if (a[i].dad == 0) {
            return i;
        }
    }
    return 0;
}

void SetLevel(vector<Node> &a, int index, int level)
{
    if (index > 0) {
        a[index].level = level;
        SetLevel(a, a[index].left, level + 1);
        SetLevel(a, a[index].right, level + 1);
    }
}

int CalcDist(const vector<Node> &a, int i, int j)
{
    if (i == j) {
        return 0;
    } else if (a[i].level < a[j].level) {
        int dist = CalcDist(a, i, a[j].dad);
        return dist + 1;
    } else {
        int dist = CalcDist(a, a[i].dad, j);
        return dist + 1;
    }
}

void CalcDist(vector<vector<int> > &d, const vector<Node> &a)
{
    for (int i = 1; i < d.size(); i++) {
        for (int j = i; j < d.size(); j++) {
            d[i][j] = d[j][i] = CalcDist(a, i, j);
        }
    }
}

int FindBest(const vector<vector<int> > &d, const vector<Node> &a)
{
    int mn = INT_MAX;
    for (int i = 1; i < d.size(); i++) {
        int dist = 0;
        for (int j = 1; j < d.size(); j++) {
            dist += d[i][j] * a[j].value;
        }
        if (mn > dist) {
            mn = dist;
        }
    }
    return mn;
}

int main()
{
    // freopen("1.txt", "r", stdin);
    int n;
    cin >> n;
    vector<Node> a(n + 1);
    for (int i = 1; i <= n; i++) {
        cin >> a[i].value;
        cin >> a[i].left;
        cin >> a[i].right;
        a[a[i].left].dad = i;
        a[a[i].right].dad = i;
    }
    int root = FindRoot(a);
    // cout << "root=" << root << endl;
    SetLevel(a, root, 0);
    // ShowTree(a);
    vector<vector<int> > d(n + 1, vector<int>(n + 1));
    CalcDist(d, a); // 计算所有两点间的距离
    cout << FindBest(d, a);
    return 0;
}