Choose the best route
Problem Description
One
day , Kiki wants to visit one of her friends. As she is liable to
carsickness , she wants to arrive at her friend’s home as soon as
possible . Now give you a map of the city’s traffic route, and the
stations which are near Kiki’s home so that she can take. You may
suppose Kiki can change the bus at any station. Please find out the
least time Kiki needs to spend. To make it easy, if the city have n bus
stations ,the stations will been expressed as an integer 1,2,3…n.
Input
There are several test cases.
Each case begins with three integers n, m and s,(n<1000,m<20000,1=<s<=n) n stands for the number of bus stations in this city and m stands for the number of directed ways between bus stations .(Maybe there are several ways between two bus stations .) s stands for the bus station that near Kiki’s friend’s home.
Then follow m lines ,each line contains three integers p , q , t (0<t<=1000). means from station p to station q there is a way and it will costs t minutes .
Then a line with an integer w(0<w<n), means the number of stations Kiki can take at the beginning. Then follows w integers stands for these stations.
Each case begins with three integers n, m and s,(n<1000,m<20000,1=<s<=n) n stands for the number of bus stations in this city and m stands for the number of directed ways between bus stations .(Maybe there are several ways between two bus stations .) s stands for the bus station that near Kiki’s friend’s home.
Then follow m lines ,each line contains three integers p , q , t (0<t<=1000). means from station p to station q there is a way and it will costs t minutes .
Then a line with an integer w(0<w<n), means the number of stations Kiki can take at the beginning. Then follows w integers stands for these stations.
Output
The
output contains one line for each data set : the least time Kiki needs
to spend ,if it’s impossible to find such a route ,just output “-1”.
Sample Input
5 8 5
1 2 2
1 5 3
1 3 4
2 4 7
2 5 6
2 3 5
3 5 1
4 5 1
2
2 3
4 3 4
1 2 3
1 3 4
2 3 2
1
1
Sample Output
1
-1
1 #include<cstdio> 2 #include<cstring> 3 #include<queue> 4 #include<vector> 5 #include<algorithm> 6 using namespace std; 7 8 struct edge 9 { 10 int u,v,w; 11 edge(int u,int v,int w):u(u),v(v),w(w){}; 12 }; 13 14 struct heapnode 15 { 16 int u,d; 17 bool operator < (const heapnode& temp)const 18 { 19 return d>temp.d; 20 } 21 }; 22 23 vector<int>G[1005]; 24 vector<edge>edges; 25 const int inf=0x3f3f3f3f; 26 int vis[1005]; 27 int d[1005]; 28 int ed; 29 int m,n; 30 31 void init() 32 { 33 for(int i=1;i<=m;i++) 34 G[i].clear(); 35 edges.clear(); 36 } 37 38 void addedge(int u,int v,int w) 39 { 40 edges.push_back(edge(u,v,w)); 41 int m=edges.size(); 42 G[u].push_back(m-1); 43 } 44 45 void dijkstra(int ed) 46 { 47 memset(vis,0,sizeof(vis)); 48 priority_queue<heapnode>q; 49 q.push((heapnode){ed,0}); 50 for(int i=1;i<=m;i++) 51 d[i]=inf; 52 d[ed]=0; 53 while(!q.empty()) 54 { 55 int u=q.top().u; 56 q.pop(); 57 if(vis[u]) 58 continue; 59 vis[u]=1; 60 for(int i=0;i<G[u].size();i++) 61 { 62 edge& e=edges[G[u][i]]; 63 if(d[e.v]>d[u]+e.w) 64 { 65 d[e.v]=d[u]+e.w; 66 q.push((heapnode){e.v,d[e.v]}); 67 } 68 } 69 } 70 } 71 72 int main() 73 { 74 int st,a,b,c,num; 75 while(scanf("%d%d%d",&m,&n,&ed)!=EOF) 76 { 77 init(); 78 for(int i=0;i<n;i++) 79 { 80 scanf("%d%d%d",&a,&b,&c); 81 addedge(b,a,c); 82 } 83 dijkstra(ed); 84 scanf("%d",&num); 85 int ans=inf; 86 while(num--) 87 { 88 scanf("%d",&st); 89 ans=min(ans,d[st]); 90 } 91 if(ans==inf) 92 printf("-1 "); 93 else 94 printf("%d ",ans); 95 } 96 return 0; 97 }