python/TangDou/Topic/P1828.cpp

#include <bits/stdc++.h>
using namespace std;
const int N = 814;
const int INF = 0x3f3f3f3f;
int id[N];
int a, b, c, g[N][N], res = INF;
int main() {
#ifndef ONLINE_JUDGE
    freopen("P1828_11.in", "r", stdin);
    // 参考答案：8
#endif
    // 加快读入
    ios::sync_with_stdio(false), cin.tie(0);
    int p, n, m; // p只奶牛，n个牧场，m条边
    cin >> p >> n >> m;

    memset(g, 0x3f, sizeof g);
    for (int i = 1; i <= n; i++) g[i][i] = 0; // 初始化

    for (int i = 1; i <= p; i++) cin >> id[i]; // i号奶牛，在id[i]这个牧场

    while (m--) {
        cin >> a >> b >> c;
        g[a][b] = g[b][a] = min(c, g[a][b]);
    }
    // 标准的Floyd板子
    for (int k = 1; k <= n; k++)
        for (int i = 1; i <= n; i++) {
            if (g[i][k] == INF) continue; // floyd小优化
            for (int j = 1; j <= n; j++)
                if (g[i][j] > g[i][k] + g[k][j])
                    g[j][i] = g[i][j] = g[i][k] + g[k][j];
        }

    for (int i = 1; i <= n; i++) { // 每个牧场出发
        int ans = 0;
        for (int j = 1; j <= p; j++) ans += g[i][id[j]];
        if (ans >= 0) res = min(res, ans);
    }
    printf("%d", res);
    return 0;
}