hdu1307Hash

题意：给定起点和终点的n为坐标及一系列n为坐标，问是否能从起点走到终点；

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StreamTokenizer;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.NavigableSet;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Scanner;
import java.util.Set;
import java.util.SortedSet;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeSet;



public class Main {


    public static void main(String[] args) throws IOException{

           StreamTokenizer cin = new StreamTokenizer(new BufferedInputStream(System.in)); 
           InputReader in = new InputReader(System.in)  ;
           PrintWriter out = new PrintWriter(System.out) ;



           int n  , t = 1 ;
           while((n = in.nextInt()) != 0){
                new Task().solve(t++ , n , in, out)  ;  // out.flush() ;
           }

           out.flush() ; 


    }


}

class Task{

          int n   ;
          HashMap<Integer, ArrayList<Integer>> adj  = new HashMap<Integer, ArrayList<Integer>>() ;
          HashSet<Integer> hash = new HashSet<Integer>() ;

          int   read(InputReader in){
                int sum = 0 , k ;
                for(int i = 0 ; i < n ; i++){
                     k = in.nextInt() ;
                     if(k == -1) return -1 ;
                     sum = sum * 10 + k ;
                }
                return sum ;
          }


          int S , T ;

          boolean dfs(int now){            
                  if(now == T) return true ;

                  hash.add(now) ;
                  ArrayList<Integer> g = adj.get(now) ;
                  if(g == null) return false ;

                  for(int v : g){
                       if(! hash.contains(v)){
                            if(dfs(v)) return true ;
                       }
                  }

                  return false ;
          }


          public void solve(int testcas , int n , InputReader  in , PrintWriter out) throws IOException{
                 this.n = n  ;
                 S = read(in) ; T = read(in) ;

                 int s , t ;
                 while((s = read(in)) != -1){
                      t = read(in) ;
                      if(adj.get(s) == null) adj.put(s, new ArrayList<Integer>()) ;
                      adj.get(s).add(t) ;

                      if(adj.get(t) == null) adj.put(t, new ArrayList<Integer>()) ;
                      adj.get(t).add(s) ;
                 }

                 if(dfs(S)) out.println("Maze #" + testcas + " can be travelled")  ;
                 else out.println("Maze #" + testcas + " cannot be travelled")  ;

          }

}


class InputReader{
        public BufferedReader  reader;
        public StringTokenizer  tokenizer;

        public InputReader(InputStream stream){
                    reader = new BufferedReader(new InputStreamReader(stream), 32768) ;
                    tokenizer = null ;
        }

        public String next(){
                    while(tokenizer == null || ! tokenizer.hasMoreTokens()){
                        try{
                                tokenizer = new StringTokenizer(reader.readLine());
                        }catch (IOException e) {
                                throw new RuntimeException(e);
                        }
                    }
                    return tokenizer.nextToken();
        }

        public int nextInt() {
                    return Integer.parseInt(next());
        }

        public long nextLong() {
                    return Long.parseLong(next());
        }

}