hdu 2680 Choose the best route

#include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <stack>#include <set>#include <map>#include <string>#include <math.h>#include <stdlib.h>#include <time.h>using namespace std;const int inf=1024;const int N=1024;int n,m,vis[N],edge[N][N],dist[N];void Dijkstra(int v0){    int i,j,k,u,minx;    for(i=1; i<=n; i++)    {        dist[i]=edge[v0][i];        vis[i]=0;    }    vis[v0]=1;    dist[v0]=0;    for(i=1; i<n; i++)    {        minx=inf,u=v0;        for(j=1; j<=n; j++)        {            if(!vis[j]&&dist[j]<minx)            {                minx=dist[j];                u=j;            }        }        vis[u]=1;        for(k=1; k<=n; k++)        {            if(!vis[k]&&edge[u][k]<inf&&dist[u]+edge[u][k]<dist[k])                dist[k]=dist[u]+edge[u][k];        }    }}int main(){    int i,j,k,u,v,w,t,ans,a,s;    while(~scanf("%d%d%d",&n,&m,&s))    {        memset(edge,0,sizeof(edge));        for(i=0; i<m; i++)        {            scanf("%d%d%d",&u,&v,&w);            if(edge[v][u]==0||edge[v][u]>w)                edge[v][u]=w;        }        for(i=1; i<=n; i++)            for(j=1; j<=n; j++)            {                if(i==j) edge[i][j]=0;                else if(edge[i][j]==0) edge[i][j]=inf;            }        scanf("%d",&w);        ans=inf;        Dijkstra(s);        for(i=0; i<w; i++)        {            scanf("%d",&a);            ans=min(ans,dist[a]);        }        if(ans<inf) printf("%d\n",ans);        else printf("-1\n");    }    return 0;}