A Walk Through the Forest dijkstra(邻接矩阵)

http://acm.hdu.edu.cn/showproblem.php?pid=1142
dijkstra(邻接矩阵)
 1 #include <cstdio>
 2 #include <cstring>
 3 #include <iostream>
 4 using namespace std;
 5 const int INF=1<<29;
 6 const int MAXN=1000+5;
 7 int v[MAXN],d[MAXN];
 8 int w[MAXN][MAXN];
 9 int n,m;
10 void dijkstra()
11 {
12     memset(v,0,sizeof(v));
13     for(int i=1;i<=n;i++) d[i]=INF;
14     d[2]=0;
15     for(int i=1;i<=n;i++)
16     {
17         int x,m=INF;
18         for(int y=1;y<=n;y++) if(!v[y]&&d[y]<=m) m=d[x=y];
19         v[x]=1;
20         for(int y=1;y<=n;y++) if(d[y]>d[x]+w[x][y]) d[y]=d[x]+w[x][y];
21     }
22 }
23 int roat[MAXN];
24 int dfs(int i)
25 {
26     int j,ans=0;
27     if(roat[i]!=0) return roat[i];
28     if(i==2) return 1;
29     for(j=1;j<=n;j++) if(w[i][j]!=INF&&d[i]>d[j])
30     {
31         roat[j]=dfs(j);
32         ans+=dfs(j);
33     }
34    return roat[i]=ans;
35 }
36 int main()
37 {
38     int i,j,a,b,wl;
39     while(cin>>n&&n)
40     {
41         cin>>m;
42         for(i=1;i<=n;i++)
43         for(j=1;j<=n;j++)
44             w[i][j]=INF;
45         for(i=0;i<m;i++) {scanf("%d%d%d",&a,&b,&wl);w[a][b]=wl;w[b][a]=wl;}
46         dijkstra();
47         memset(roat,0,sizeof(roat));
48         dfs(1);
49         cout<<roat[1]<<endl;
50     }
51     return 0;
52 }