1 #include<cstdio>
2 #include<iostream>
3 #include<algorithm>
4 #include<cstring>
5
6 using namespace std;
7 const int inf = 0x3f3f;
8 int n, c, ts, te, dis[2505], vis[2505], g[5005][5005];
9
10 inline void dijkstra(int x){
11 for(int i = 1; i <= n; i++) dis[i] = (i == x ? 0 : inf);
12 for(int i = 1; i <= n; i++){
13 int t = 0, y = inf;
14 for(int j = 1; j <= n; j++) if(!vis[j] && dis[j] <= y) y = dis[t = j];
15 vis[t] = 1;
16 for(int j = 1; j <= n; j++) dis[j] = min(dis[j], dis[t] + g[t][j]);
17 }
18 }
19
20
21 int main(){
22 memset(g, 0x3f3f, sizeof(g));//初始化！！
23 scanf("%d%d%d%d", &n, &c, &ts, &te);
24 for(int i = 1; i <= c; i++){
25 int u, v, w;
26 scanf("%d%d%d", &u, &v, &w);
27 g[u][v] = g[v][u] = w;
28 }
29 dijkstra(ts);
30 printf("%d", dis[te]);
31 return 0;
32 }
