URAL1077[Travelling tours]

图论，在图中找尽可能多的环，且一个环的边的集合不是其它环的边的集合的子集。

然后，具体操作有看题解，所以我没必要讲了。

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;

#include <map>

//using std::map;

using std::pair;

using std::make_pair;

#include <algorithm>

using std::sort;

#include <cassert>

//using std::assert;

 

class Application

{

      int N,M;

      vector<vector<bool> > map;

      vector<vector<bool> > spaning_tree;

      vector<bool> visited;

      vector<int> path;

      void dfs(int node)

      {

           visited[node]=true;

           for (int i=0;i<N;i++)

               if (map[node][i]&&(!visited[i]))

               {

                  map[node][i]=false;

                  map[i][node]=false;

                  spaning_tree[node][i]=true;

                  spaning_tree[i][node]=true;

                  dfs(i);

               }

      }

      void print(int node,const int& end)

      {

           if (!visited[node])

           {

              visited[node]=true;

              path.push_back(node);

              if (node==end)

              {

                 cout<<path.size();

                 for (int i=0;i<path.size();i++) cout<<” “<<path[i]+1;

                 cout<<endl;

              }

              for (int i=0;i<N;i++)

                  if (spaning_tree[node][i])

                     print(i,end);

              path.pop_back();

              visited[node]=false;

           }

      }

      public:

      Application()

      {

                    cin>>N>>M;

                    map.resize(N,vector<bool>(N,false));

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

                    {

                        int u,v;

                        cin>>u>>v;

                        map[u-1][v-1]=map[v-1][u-1]=true;

                    }

      }

      int run()

      {

          spaning_tree.resize(N,vector<bool>(N,false));

          visited.resize(N,false);

          int part=0;

          for (int i=0;i<N;i++)

              if (!visited[i]) dfs(i),part++;

          cout<<M-N+part<<endl;

         

          visited=vector<bool>(N,false);

          for (int i=0;i<N;i++)

              for (int j=i+1;j<N;j++)

                  if (map[i][j])

                     print(i,j);

          return 0;

      }

};

 

int main()

{

    Application app;

    return app.run();

}