Light oj 1002 Country Roads (Dijkstra)

 1 #include <algorithm>
 2 #include <iostream>
 3 #include <cstdio>
 4 #include <cstring>
 5 using namespace std;
 6 
 7 const int maxn = 510;
 8 const int INF = 0x3f3f3f3f;
 9 int map[maxn][maxn], dist[maxn];
10 void init ()
11 {
12     int i, j;
13     for (i=0; i<maxn; i++)
14         for (j=0; j<maxn; j++)
15             if (i==j)
16                 map[i][j] = 0;
17             else
18                 map[i][j] = INF;
19 }
20 void dijkstra (int s, int n)
21 {
22     int i, j, vis[maxn];
23     memset (vis, 0, sizeof(vis));
24 
25     for (i=0; i<n; i++)
26         dist[i] = map[s][i];
27     vis[s] = 1;
28 
29     for (i=1; i<n; i++)
30     {
31         int mini = INF, index;
32         for (j=0; j<n; j++)
33             if (!vis[j] && mini > dist[j])
34             {
35                 mini = dist[j];
36                 index = j;
37             }
38             if (mini == INF)
39                 return ;
40         vis[index] = 1;
41         for (j=0; j<n; j++)
42             if (!vis[j])
43             {
44                 dist[j] = min(dist[j], max(map[index][j],dist[index]));//重点
45             }
46     }
47 }
48 int main ()
49 {
50     int T, n, m, l = 1;
51     scanf ("%d", &T);
52     while (T --)
53     {
54         init ();
55         scanf ("%d %d", &n, &m);
56         while (m --)
57         {
58             int u, v, w;
59             scanf ("%d %d %d", &u, &v, &w);
60             if (map[u][v] > w)//有重边，选最优
61             map[u][v] = map[v][u] = w;
62         }
63         int t;
64         scanf ("%d", &t);
65         dijkstra (t, n);
66         printf ("Case %d:\n", l ++);
67         for (int i=0; i<n; i++)
68             if (dist[i] != INF)
69                 printf ("%d\n", dist[i]);
70             else
71                 printf ("Impossible\n");
72     }
73     return 0;
74 }