Invitation Cards -向前星建图-堆优化dijkstra

• Invitation Cards

•  POJ - 1511 
• 正反建图
• 跑两边最短路即可。

• #include<stdio.h>
  #include<queue>
  #include<vector>
  #include<cstring>
  #include<iostream>
  using namespace std;
  #define maxn 8000500
  #define ll long long
  #define inf 0x3f3f3f3f
  struct node
  {
      ll v,w;
      bool operator <(const node &a)const
      {
          return w>a.w;
      }
  } dis1[maxn],dis2[maxn];
  struct head
  {
      int to,ord,w;
  } edge[maxn];
  bool vis[maxn];
  ll n,m,t,x,y,z,ans,len,top,he1[maxn],he2[maxn],cnt,temp;
  void dij(ll *he,node *dis)
  {
      dis[1].w=0;
      priority_queue<node>q;
      q.push(dis[1]);
      while(!q.empty())
      {
          top=q.top().v;
          q.pop();
          vis[top]=0;
          for(int i=he[top]; i!=-1; i=edge[i].ord)
          {
              temp=edge[i].to;
              if(dis[temp].w>dis[top].w+edge[i].w)
              {
                  dis[temp].w=dis[top].w+edge[i].w;
                  if(!vis[temp])
                  {
                      vis[temp]=1;
                      q.push(dis[temp]);
                  }
              }
          }
      }
  }
  void add(int x,int y,int z)
  {
      ++cnt;
      edge[cnt].ord=he1[x];
      edge[cnt].to=y;
      edge[cnt].w=z;
      he1[x]=cnt;
  }
  void add2(int x,int y,int z)
  {
      ++cnt;
      edge[cnt].ord=he2[x];
      edge[cnt].to=y;
      edge[cnt].w=z;
      he2[x]=cnt;
  }
  int main()
  {
      scanf("%lld",&t);
      while(t--)
      {
          ans=cnt=0;
          scanf("%lld%lld",&n,&m);
          for(int i=1; i<=n; i++)
          {
              dis1[i].w=inf;
              dis1[i].v=i;
              dis2[i].w=inf;
              dis2[i].v=i;
              vis[i]=0;
              he1[i]=-1;
              he2[i]=-1;
          }
          while(m--)
          {
              scanf("%lld%lld%lld",&x,&y,&z);
              add(x,y,z);
              add2(y,x,z);
          }
          dij(he1,dis1);
          dij(he2,dis2);
          for(int i=2; i<=n; i++)
              ans+=dis1[i].w+dis2[i].w;
          printf("%lld\n",ans);
      }
      return 0;
  }
  

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