题意：







思路：

裸的Dijkstra 爆敲一发模板

//By SiriusRen

#include <queue>

#include <cstdio>

#include <cstring>

#include <algorithm>

using namespace std;

#define N 2222

int f,p,c,m,xx,yy,zz,w[N],v[N],next[N],first[N],tot,dis[N],vis[N],ans,s[N];

struct Node{int now,weight;}jy;

priority_queue<Node>pq;

void add(int x,int y,int z){

    w[tot]=z,v[tot]=y,next[tot]=first[x],first[x]=tot++;

}

bool operator < (Node a,Node b){

    return a.weight>b.weight;

}

void Dijkstra(){

    memset(dis,0x3f,sizeof(dis));

    dis[1]=0;

    jy.now=1,jy.weight=0;

    pq.push(jy);

    while(!pq.empty()){

        Node t=pq.top();pq.pop();

        if(vis[t.now])continue;

        vis[t.now]=1;

        for(int i=first[t.now];~i;i=next[i])

            if(!vis[v[i]]&&dis[v[i]]>dis[t.now]+w[i]){

                dis[v[i]]=dis[t.now]+w[i];

                jy.now=v[i],jy.weight=dis[v[i]];

                pq.push(jy);

            }

    }

}

int main(){

    memset(first,-1,sizeof(first));

    scanf("%d%d%d%d",&f,&p,&c,&m);

    for(int i=1;i<=p;i++){

        scanf("%d%d%d",&xx,&yy,&zz);

        add(xx,yy,zz),add(yy,xx,zz);

    }

    Dijkstra();

    for(int i=1;i<=c;i++){

        scanf("%d",&xx);

        if(dis[xx]<=m)

            s[++ans]=i;

    }

    printf("%d\n",ans);

    for(int i=1;i<=ans;i++)

        printf("%d\n",s[i]);

}