【最短路】【Heap-Dijkstra】【分层图】bzoj2662 [BeiJing wc2012]冻结

裸的分层图最短路。

 #include<cstdio>
 #include<cstring>
 #include<queue>
 #include<algorithm>
 using namespace std;
 #define N 51
 #define K 51
 #define M 2001
 struct Point{int u,d;Point(const int &a,const int &b){d=a;u=b;}Point(){}};
 bool operator < (const Point &a,const Point &b){return a.d>b.d;}
 priority_queue<Point>q;
 int n,m,k,dis[N*K],ans=;
 bool vis[N*K];
 int first[M*K*],next[M*K*],v[M*K*],w[M*K*],en,x,y,z;
 void AddEdge(const int &U,const int &V,const int &W)
 {
     v[++en]=V;
     w[en]=W;
     next[en]=first[U];
     first[U]=en;
 }
 void dijkstra(const int &s)
 {
     memset(dis,0x7f,sizeof(dis));
     dis[s]=; q.push(Point(,s));
     while(!q.empty())
       {
         Point x=q.top(); q.pop();
         if(!vis[x.u])
           {
             vis[x.u]=;
             for(int i=first[x.u];i;i=next[i])
               if(dis[v[i]]>dis[x.u]+w[i])
                 {
                   dis[v[i]]=dis[x.u]+w[i];
                   q.push(Point(dis[v[i]],v[i]));
                 }
           }
       }
     for(int i=;i<=k;i++) ans=min(ans,dis[n+i*n]);
     printf("%d\n",ans);
 }
 int main()
 {
     scanf("%d%d%d",&n,&m,&k);
     for(int i=;i<=m;i++)
       {
         scanf("%d%d%d",&x,&y,&z);
         AddEdge(x,y,z); AddEdge(y,x,z);
         for(int j=;j<=k;j++)
           {
             AddEdge(x+j*n,y+j*n,z);
             AddEdge(y+j*n,x+j*n,z);
             AddEdge(x+(j-)*n,y+j*n,z>>);
             AddEdge(y+(j-)*n,x+j*n,z>>);
           }
       }
     dijkstra();
     return ;
 }