1 #include <cstdio>
 2 #include <cstring>
 3 #include <vector>
 4 #include <queue>
 5 #include <algorithm>
 6 using namespace std;
 7 
 8 const int maxn = 1050;
 9 const int INF = 0x7ffffff;
10 
11 struct Edge {
12     int from, to, dist;
13     Edge(int u, int v, int d) :from(u), to(v), dist(d) {}
14 };
15 
16 struct HeapNode {
17     int d, u;
18     HeapNode(int dv, int uv) :d(dv), u(uv){}
19     bool operator < (const HeapNode& rhs) const {
20         return d > rhs.d;
21     }
22 };
23 struct Dijkstra {
24     int n, m;
25     Dijkstra(){};
26     Dijkstra(int nv, int mv) :n(nv), m(mv){}
27     vector<Edge> edges;
28     vector<int> G[maxn];
29     bool done[maxn]; //是否已永久标号
30     int d[maxn]; //s到各个点的距离
31     //int p[maxn]; //最短路中的上一条弧
32     void init(int n) {
33         this->n = n;
34         for (int i = 0; i < n; i++) G[i].clear();
35         edges.clear();
36     }
37     void AddEdge(Edge e) {
38         edges.push_back(e);
39         m = edges.size();
40         G[e.from].push_back(m - 1);
41     }
42     void dijkstra(int s) {
43         priority_queue<HeapNode> Q;
44         for (int i = 0; i < n; i++) d[i] = INF;
45         d[s] = 0;
46         memset(done, 0, sizeof(done));
47         Q.push(HeapNode(0, s));
48         while (!Q.empty()) {
49             HeapNode x = Q.top(); Q.pop();
50             int u = x.u;
51             if (done[u]) continue;
52             done[u] = true;
53             for (int i = 0; i < G[u].size(); i++) {
54                 Edge& e = edges[G[u][i]];
55                 if (d[e.to] > d[u] + e.dist) {
56                     d[e.to] = d[u] + e.dist;
57                     //p[e.to] = G[u][i];
58                     Q.push(HeapNode(d[e.to],e.to));
59                 }
60             }
61         }
62     }
63 };
64 
65 int main()
66 {
67     int m, n, a, b, r,ans,temp,s,t;
68     Dijkstra d;
69     while (scanf("%d%d", &n, &m) == 2)
70     {
71         ans = 0;
72         d.n=n; d.init(n);
73         for (int i = 0; i < m; i++)
74         {
75             scanf("%d%d%d", &a, &b, &r);
76             d.AddEdge(Edge(a, b, r));
77             d.AddEdge(Edge(b, a, r));
78         }
79         scanf("%d%d",&s,&t);
80         d.dijkstra(s);
81         if(d.d[t]!=INF) printf("%d\n", d.d[t]);
82         else  printf("-1\n");
83     }
84 }