题目

代码 

#include <bits/stdc++.h>
using namespace std;
#define x first
#define y second
typedef pair<int, int> PII;
const int N = 5e4+10, M = 2e5+10;
const int inf = 0x3f3f3f3f; 
int n, m;
int a[6];
int h[N], e[M], ne[M], idx, w[M];
int dist[6][N];
int st[N];
unordered_map<int, int> mp;
void add(int a, int b, int c)  // 添加一条边a->b
{
    w[idx] = c, e[idx] = b, ne[idx] = h[a], h[a] = idx ++ ;
}
void dijkstra(int s, int d[])
{
    memset(st, 0, sizeof st);
    priority_queue<PII, vector<PII>, greater<PII>> q;
    q.push({0, s}); d[s] = 0; st[s] = true;

    while(q.size())
    {
        int u = q.top().y; q.pop();
        st[u] = false;
        
        for(int i = h[u]; ~i; i = ne[i])
        {
            int j = e[i];
            if(d[j] > d[u] + w[i])
            {
                d[j] = d[u] + w[i];
                if(!st[j]) q.push({d[j], j}), st[j] = true;
            }
        }
    }
}
void out()
{
    for(int i = 0; i <= 5; i++)
        cout << a[i] << ' ';
    cout << '\n';
}
int main()
{
    cin >> n >> m;
    a[0] = 1, mp[1] = 0;
    for(int i = 1; i <= 5; i++)
    {
        cin >> a[i];
        mp[a[i]] = i;
    }
        
    memset(h, -1, sizeof h);
    for(int i = 1; i <= m; i++)
    {
        int x, y, t;
        cin >> x >> y >> t;
        add(x, y, t);
        add(y, x, t);
    }
    
    memset(dist, 0x3f, sizeof dist);
    for(int i = 0; i <= 5; i++)
        dijkstra(a[i], dist[i]);
    
    sort(a+1, a+6);
    int ans = inf;
    do{
        int sum = 0;
        for(int i = 0; i+1 <= 5; i++)
        {
            int t = dist[mp[a[i]]][a[i+1]];
            if(t == inf)
            {
                sum = inf;
                break;
            }
            sum += t;
        }
        ans = min(ans, sum);
    }while(next_permutation(a+1, a+6));
    
    cout << ans;
}

注意

起点永远是1

要先sort一下，不然permutation可能没有枚举完