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

裸的分层图最短路。

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<queue>
 4 #include<algorithm>
 5 using namespace std;
 6 #define N 51
 7 #define K 51
 8 #define M 2001
 9 struct Point{int u,d;Point(const int &a,const int &b){d=a;u=b;}Point(){}};
10 bool operator < (const Point &a,const Point &b){return a.d>b.d;}
11 priority_queue<Point>q;
12 int n,m,k,dis[N*K],ans=2147483647;
13 bool vis[N*K];
14 int first[M*K*2],next[M*K*2],v[M*K*2],w[M*K*2],en,x,y,z;
15 void AddEdge(const int &U,const int &V,const int &W)
16 {
17     v[++en]=V;
18     w[en]=W;
19     next[en]=first[U];
20     first[U]=en;
21 }
22 void dijkstra(const int &s)
23 {
24     memset(dis,0x7f,sizeof(dis));
25     dis[s]=0; q.push(Point(0,s));
26     while(!q.empty())
27       {
28         Point x=q.top(); q.pop();
29         if(!vis[x.u])
30           {
31             vis[x.u]=0;
32             for(int i=first[x.u];i;i=next[i])
33               if(dis[v[i]]>dis[x.u]+w[i])
34                 {
35                   dis[v[i]]=dis[x.u]+w[i];
36                   q.push(Point(dis[v[i]],v[i]));
37                 }
38           }
39       }
40     for(int i=0;i<=k;i++) ans=min(ans,dis[n+i*n]);
41     printf("%d\n",ans);
42 }
43 int main()
44 {
45     scanf("%d%d%d",&n,&m,&k);
46     for(int i=1;i<=m;i++)
47       {
48         scanf("%d%d%d",&x,&y,&z);
49         AddEdge(x,y,z); AddEdge(y,x,z);
50         for(int j=1;j<=k;j++)
51           {
52             AddEdge(x+j*n,y+j*n,z);
53             AddEdge(y+j*n,x+j*n,z);
54             AddEdge(x+(j-1)*n,y+j*n,z>>1);
55             AddEdge(y+(j-1)*n,x+j*n,z>>1);
56           }
57       }
58     dijkstra(1);
59     return 0;
60 }