URAL1080[Map Colouring]

判断此图是否可能为二分图。

然后DFS染色就OK了。

CODE:

/*

PROGRAM: $PROGRAM

AUTHOR: Su Jiao

DATE: 2010-4-10

DESCRIPTION:

$DESCRIPTION

*/

#include <iostream>

using std::cin;

using std::cout;

#include <fstream>

using std::ifstream;

using std::ofstream;

#include <sstream>

using std::stringstream;

using std::endl;

#include <vector>

using std::vector;

#include <string>

using std::string;

#include <stack>

using std::stack;

#include <queue>

using std::queue;

using std::priority_queue;

#include <set>

using std::set;

#include <map>

using std::map;

using std::pair;

using std::make_pair;

#include <algorithm>

using std::sort;

#include <cassert>

//using std::assert;

 

class Application

{

      static const int RED=0;

      static const int BLUE=1;

      static const int NOTCOLORED=-1;

      int N;

      vector<vector<int> > link;

      vector<int> color;

      bool color_it(int who,int with)

      {

           if (color[who]!=NOTCOLORED)

              return color[who]==with;

           else

           {

               color[who]=with;

               for (int i=0;i<link[who].size();i++)

                   if (!color_it(link[who][i],with==RED?BLUE:RED)) return false;

               return true;

           }

      }

      public:

      Application()

      {

                   cin>>N;

                   link.resize(N);

                   for (int i=0;i<N;i++)

                   {

                       int get;

                       for (;;)

                       {

                           cin>>get;

                           if (get)

                           {

                              link[i].push_back(get-1);

                              link[get-1].push_back(i);

                           }

                           else break;

                       }

                   }

      }

      int run()

      {

          bool can_color_it_in_red_and_blue=true;

          color.resize(N,NOTCOLORED);

          for (int i=0;i<N;i++)

              if (color[i]==NOTCOLORED)

                 if (!color_it(i,RED))

                 {

                    can_color_it_in_red_and_blue=false;

                    break;

                 }

          if (can_color_it_in_red_and_blue)

          {

             for (int i=0;i<N;i++)

                 cout<<color[i];

             cout<<endl;

          }

          else cout<<-1<<endl;

          return 0;

      }

};

 

int main()

{

    Application app;

    return app.run();

}