P1266 速度限制

 1 #include <iostream>
 2 #include <cstring>
 3 #include <queue>
 4 using namespace std;
 5 const int N = 160,M = N*N,INF = 0x3f3f3f3f,S = 510;
 6 typedef pair<int,int> PII;
 7 int n,m,e,idx,h[N];
 8 PII pre[N][S];
 9 double dist[N][S];
10 bool st[N][S];
11 struct Road{
12     int to,ne,v,L;
13 }road[M];
14 struct Node{
15     double t;
16     int u,vs;
17     bool operator>(const Node& s)const{
18         return this->t>s.t;
19     }
20 };
21 void add(int a,int b,int v,int l)
22 {
23     road[idx].to = b,road[idx].v = v,road[idx].L = l,road[idx].ne = h[a],h[a] = idx++;
24 }
25 void dijkstra(int s) 
26 {
27     for(int i=1;i<=n;i++)
28       for(int j=0;j<=500;j++) dist[i][j] = INF; 
29     dist[s][70] = 0;
30     priority_queue<Node,vector<Node>,greater<Node> > q;
31     q.push({0,s,70});
32     while(q.size())
33     {
34         Node it = q.top();
35         q.pop();
36         int u = it.u,speed = it.vs;
37         if(st[u][speed]) continue;
38         st[u][speed] = 1;
39         for(int i=h[u];~i;i=road[i].ne)
40         {
41             int v = road[i].to,L = road[i].L,limit = road[i].v;
42             int new_v = !limit?speed:limit;
43             double new_t = L*1.0/new_v;
44             if(dist[v][new_v]>dist[u][speed]+new_t) 
45             {
46                 dist[v][new_v] = dist[u][speed]+new_t;
47                 pre[v][new_v] = {u,speed};
48                 q.push({dist[v][new_v],v,new_v});
49             }
50         }
51     }
52 }
53 void dfs(int u,int v)
54 {
55     if(u==-1) return;
56     dfs(pre[u][v].first,pre[u][v].second);
57     printf("%d ",u);
58 }
59 int main()
60 {
61     scanf("%d%d%d",&n,&m,&e);
62     memset(h,-1,sizeof h);
63     memset(pre,-1,sizeof pre);
64     while(m--)
65     {
66         int a,b,v,l;
67         scanf("%d%d%d%d",&a,&b,&v,&l);
68         add(a,b,v,l);
69     }
70     dijkstra(0);
71     double minv = INF;int tar_v;
72     for(int i=0;i<=500;i++)
73        if(dist[e][i]<minv)
74        {
75                tar_v = i;
76                minv = dist[e][i];
77        }
78     dfs(e,tar_v);
79     printf("\n");
80     return 0;
81 }