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 }