HDu2680（Choose the best route）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=2680

 

package graph_ShortestPath;//思路：构建反向图。import java.util.*;import java.io.*;public class HDU2680 {static int[][]map;static int[]dist;static int n;public static void main(String[] args) throws IOException {//Scanner sc = new Scanner(System.in);StreamTokenizer st = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));int m,s;while(st.nextToken()!=StreamTokenizer.TT_EOF){n = (int)st.nval;st.nextToken();m = (int)st.nval; st.nextToken();s = (int)st.nval;map = new int[n+1][n+1];for (int i = 1; i <= n; i++)Arrays.fill(map[i], Integer.MAX_VALUE);dist = new int[n+1];for(int i = 0;i<m;i++){st.nextToken();int p = (int)st.nval;st.nextToken();int q = (int)st.nval;st.nextToken();int t = (int)st.nval;if(t<map[q][p])map[q][p] = t;//反向图。}st.nextToken();int num =(int)st.nval;int min = Integer.MAX_VALUE;int[]arr = new int[num+1];for(int i = 1;i<=num;i++){st.nextToken();arr[i] =(int)st.nval;}dijkstra(s);for(int i = 1;i<=num;i++){if(dist[arr[i]]<min)min = dist[arr[i]];}if(min>=Integer.MAX_VALUE)System.out.println(-1);else System.out.println(min);}}private static void dijkstra(int ss) {boolean[] p = new boolean[n+1];for(int i = 1;i<=n;i++){p[i] = false;if(i!=ss)dist[i] = map[ss][i];}p[ss] = true;dist[ss] = 0;for(int i = 0;i<n-1;i++){int min = Integer.MAX_VALUE;int k = -1;for(int j = 1;j<=n;j++){if(!p[j] && dist[j]<min){min = dist[j];k = j;}}if(k==-1)return;p[k] = true;for(int j = 1;j<=n;j++){if(!p[j] && map[k][j]!=Integer.MAX_VALUE && dist[j] > dist[k] +map[k][j])dist[j]=dist[k]+map[k][j];}}}}