luogu P1342 请柬

#include<cmath>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#define ll long long
#define re register
#define il inline
#define inf 214748364
#define fp(i,a,b) for(re int i=a;i<=b;i++)
#define fq(i,a,b) for(re int i=a;i>=b;i--)
using namespace std;
int n,m,h[1000005],cnt=0,inq[1000005]={},dis[1000005]={},h1[1000005]={};
ll ans=0;
struct Edge
{
    int to,next,w;
}e[1000005],e1[1000005];
struct Node
{
    int l,d;
    Node(){}
    Node(int l,int d):l(l),d(d){}
    bool operator < (const Node& zsy) const
        {
            return l>zsy.l;
        }
};
il void add(re int u,re int v,re int w)
{
    e[++cnt]=(Edge){v,h[u],w};h[u]=cnt;
}
il void add1(re int u,re int v,re int w)
{
    e1[cnt]=(Edge){v,h1[u],w};h1[u]=cnt;
}
il void Dijkstra()
{
    fp(i,1,n) dis[i]=inf;
    dis[1]=0;
    priority_queue<Node>Q;
    Q.push(Node(0,1));
    while(!Q.empty())
    {
        Node u=Q.top();Q.pop();
        if(inq[u.d]) continue;
        inq[u.d]=1;
        for(re int i=h[u.d];i+1;i=e[i].next)
        {
            re int v=e[i].to,w=e[i].w;
            if(u.l+w<dis[v])
            {
                dis[v]=u.l+w;
                Q.push(Node(dis[v],v));
            }
        }
    }
}
il void Dijkstra1()
{
    fp(i,1,n) dis[i]=inf;
    dis[1]=0;
    memset(inq,0,sizeof(inq));
    priority_queue<Node>Q;
    Q.push(Node(0,1));
    while(!Q.empty())
    {
        Node u=Q.top();Q.pop();
        if(inq[u.d]) continue;
        inq[u.d]=1;
        for(re int i=h1[u.d];i+1;i=e1[i].next)
        {
            re int v=e1[i].to,w=e1[i].w;
            if(u.l+w<dis[v])
            {
                dis[v]=u.l+w;
                Q.push(Node(dis[v],v));
            }
        }
    }
}
int main()
{
    memset(h,-1,sizeof(h));memset(h1,-1,sizeof(h1));
    scanf("%lld%lld",&n,&m);
    fp(i,1,m)
    {
        ll u,v,w;
        scanf("%lld%lld%lld",&u,&v,&w);
        add(u,v,w);
        add1(v,u,w);
    }
    Dijkstra();
    fp(i,2,n) ans+=dis[i];
    Dijkstra1();
    fp(i,2,n) ans+=dis[i];
    printf("%lld\n",ans);
    return 0;
}