python/TangDou/LuoGuBook/P1364_diagram_Floyd.cpp

#include <bits/stdc++.h>

using namespace std;

const int N = 210;
const int INF = 0x3f3f3f3f;
int minn = INF;
int n, m, k;
int d[N][N]; //邻接矩阵存储
int p[N];

// 算法结束后，d[a][b]表示a到b的最短距离,k->i->j
void floyd() {
    for (int k = 1; k <= n; k++)
        for (int i = 1; i <= n; i++)
            for (int j = 1; j <= n; j++)
                d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
}


int main() {
    cin >> n;
    //floyd初始化
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++)
            if (i == j) d[i][j] = 0;
            else d[i][j] = INF;

    //读入数据
    for (int i = 1; i <= n; i++) {
        int a, b;
        cin >> p[i] >> a >> b;
        if (a) d[a][i] = d[i][a] = 1;
        if (b) d[b][i] = d[i][b] = 1;
    }
    //弗洛依德算法
    floyd();

    //模拟
    for (int i = 1; i <= n; i++) {//模拟1-n的每一个结点，尝试将医院放在这里
        int s = 0; //看看取得的”所有居民所走的路程之和“是多少，取最小值
        for (int j = 1; j <= n; j++) s += d[i][j] * p[j];
        //取最小值
        minn = min(minn, s);
    }
    cout << minn << endl;
    return 0;
}