A Walk Through the Forest dijkstra(邻接矩阵)

http://acm.hdu.edu.cn/showproblem.php?pid=1142

dijkstra(邻接矩阵)

#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
const int INF=1<<29;
const int MAXN=1000+5;
int v[MAXN],d[MAXN];
int w[MAXN][MAXN];
int n,m;
void dijkstra()
{
    memset(v,0,sizeof(v));
    for(int i=1;i<=n;i++) d[i]=INF;
    d[2]=0;
    for(int i=1;i<=n;i++)
    {
        int x,m=INF;
        for(int y=1;y<=n;y++) if(!v[y]&&d[y]<=m) m=d[x=y];
        v[x]=1;
        for(int y=1;y<=n;y++) if(d[y]>d[x]+w[x][y]) d[y]=d[x]+w[x][y];
    }
}
int roat[MAXN];
int dfs(int i)
{
    int j,ans=0;
    if(roat[i]!=0) return roat[i];
    if(i==2) return 1;
    for(j=1;j<=n;j++) if(w[i][j]!=INF&&d[i]>d[j])
    {
        roat[j]=dfs(j);
        ans+=dfs(j);
    }
   return roat[i]=ans;
}
int main()
{
    int i,j,a,b,wl;
    while(cin>>n&&n)
    {
        cin>>m;
        for(i=1;i<=n;i++)
        for(j=1;j<=n;j++)
            w[i][j]=INF;
        for(i=0;i<m;i++) {scanf("%d%d%d",&a,&b,&wl);w[a][b]=wl;w[b][a]=wl;}
        dijkstra();
        memset(roat,0,sizeof(roat));
        dfs(1);
        cout<<roat[1]<<endl;
    }
    return 0;
}