BZOJ4158 : [POI2007]Railway

#include<cstdio>
#include<algorithm>
const int N=5010,M=500010,inf=~0U>>1;
int n,m,p,i,x,f[N],id[N],ans,cnt,use[M];
int q[131072],in[N],d[N],pre[N];unsigned short h,t;
struct Edge{int v,w;Edge*nxt;}*g[N],pool[M<<1],*cur=pool,*I;
inline void add(int x,int y,int z){I=cur++;I->v=y;I->w=z;I->nxt=g[x];g[x]=I;}
struct E{int x,y,z;}e[M];
inline bool cmp(E a,E b){return a.z<b.z;}
inline void read(int&a){char c;while(!(((c=getchar())>=‘0‘)&&(c<=‘9‘)));a=c-‘0‘;while(((c=getchar())>=‘0‘)&&(c<=‘9‘))(a*=10)+=c-‘0‘;}
int F(int x){return f[x]==x?x:f[x]=F(f[x]);}
int main(){
  for(read(n),read(m);i<m;i++){
    read(e[i].x),read(e[i].y),read(e[i].z);
    add(e[i].x,e[i].y,e[i].z);
    add(e[i].y,e[i].x,e[i].z);
  }
  for(read(p),i=1;i<=p;i++)read(id[i]);
  for(i=1;i<=n;i++)d[i]=inf;
  d[q[0]=id[1]]=0,in[id[1]]=1;
  while(h!=t+1)for(I=g[x=q[h++]],in[x]=0;I;I=I->nxt)if(d[x]+I->w<d[I->v]){
    d[I->v]=d[x]+I->w,pre[I->v]=x;
    if(!in[I->v]){
      in[I->v]=1;
      if(d[I->v]<d[q[h]])q[--h]=I->v;else q[++t]=I->v;
    }
  }
  for(in[id[1]]=i=1;i<=p;i++)for(x=id[i];!in[x];x=pre[x])in[x]=1;
  for(i=1;i<=n;i++)f[i]=i;
  for(std::sort(e,e+m,cmp),i=0;i<m;i++)if(in[e[i].x]&&in[e[i].y]&&F(e[i].x)!=F(e[i].y)){
    f[f[e[i].x]]=f[e[i].y];
    ans+=e[i].z,cnt++,use[i]=1;
  }
  for(printf("%d %d\n",ans,cnt),i=0;i<m;i++)if(use[i])printf("%d %d\n",e[i].x,e[i].y);
  return 0;
}