A

 1 //Dijkstra
 2 #include <iostream>
 3 #include <algorithm>
 4 #define Faster ios_base::sync_with_stdio(false),cin.tie(0)
 5 #define Read freopen("in.txt","r",stdin),freopen("out.txt","w",stdout)
 6 #define Close fclose(stdin),fclose(stdout)
 7 const int maxn = 1000+5;
 8 const int INF = 0xfffffff;
 9 using namespace std;
10 
11 int g[maxn][maxn];
12 bool v[maxn];
13 int dis[maxn];
14 
15 int t, n;
16 
17 //x 为起点
18 void dij(int x){
19     for(int i = 0;i <= n;i++){
20         dis[i] = g[x][i];
21         v[i] = true;
22     }
23     v[x] = false;
24 
25     int Min, p;
26     for(int i = 1;i <= n;i++){
27         Min = INF;
28         for(int j = 1;j <= n;j++){
29             if(v[j] && dis[j] < Min){
30                 Min = dis[j];
31                 p = j;
32             }
33         }
34         if(Min == INF)
35             break;
36         v[p] = false;
37         for(int j = 1;j <= n;j++){
38             if(v[j] && dis[p] + g[p][j] < dis[j]){
39                 dis[j] = dis[p] + g[p][j];
40             }
41         }
42     }
43 }
44 
45 int main(){
46     Faster;
47     cin >> t >> n;
48     for(int i = 0;i <= n;i++){
49         for(int j = 0;j <= n;j++)
50             g[i][j] = INF;
51     }
52     for(int i = 0;i < t;i++){
53         int x, y, z;
54         cin >> x >> y >> z;
55         if(g[x][y] > z)
56             g[x][y] = g[y][x] = z;
57     }
58     dij(1);
59     cout << dis[n] << endl;
60     return 0;
61 }