grafo euleri code example

Example: sendero euleriano

// Implemetación en c++
#include <iostream>
#include <string.h>
#include <algorithm>
#include <list>
using namespace std;
 
// Clase para representar el grafo
class Graph
{
  private:
    int V;    // Nº de vertices
    list<int> *adj;    //vector dinámico
  public:
    // Constructor y destructor
    Graph(int V)  { this->V = V;  adj = new list<int>[V];  }
    ~Graph()      { delete [] adj;  }
 
    void addEdge(int u, int v) {  adj[u].push_back(v); adj[v].push_back(u); }
    void rmvEdge(int u, int v);
 
    void printEulerTour();
    void printEulerUtil(int s);
 
    int DFSCount(int v, bool visited[]);

    bool isValidNextEdge(int u, int v);
};
 

void Graph::printEulerTour()
{
  int u = 0;
  for (int i = 0; i < V; i++)
      if (adj[i].size() & 1)
        {   u = i; break;  }
 
  printEulerUtil(u);
  cout << endl;
}

void Graph::printEulerUtil(int u)
{

  list<int>::iterator i;
  for (i = adj[u].begin(); i != adj[u].end(); ++i)
  {
      int v = *i;

      if (v != -1 && isValidNextEdge(u, v))
      {
          cout << u << "-" << v << "  ";
          rmvEdge(u, v);
          printEulerUtil(v);
      }
  }
}
 

bool Graph::isValidNextEdge(int u, int v)
{
  int count = 0;  
  list<int>::iterator i;
  for (i = adj[u].begin(); i != adj[u].end(); ++i)
     if (*i != -1)
        count++;
  if (count == 1)
    return true;
 
 
  bool visited[V];
  memset(visited, false, V);
  int count1 = DFSCount(u, visited);
 
  rmvEdge(u, v);
  memset(visited, false, V);
  int count2 = DFSCount(u, visited);

  addEdge(u, v);

  return (count1 > count2)? false: true;
}
 

void Graph::rmvEdge(int u, int v)
{
  list<int>::iterator iv = find(adj[u].begin(), adj[u].end(), v);
  *iv = -1;

  list<int>::iterator iu = find(adj[v].begin(), adj[v].end(), u);
  *iu = -1;
}
 
int Graph::DFSCount(int v, bool visited[])
{
  // marcamos el actual
  visited[v] = true;
  int count = 1;
 
  // Metodo recursivo
  list<int>::iterator i;
  for (i = adj[v].begin(); i != adj[v].end(); ++i)
      if (*i != -1 && !visited[*i])
          count += DFSCount(*i, visited);
 
  return count;
}
 
int main()
{
  // Ejemplos
  Graph g1(4);
  g1.addEdge(0, 1);
  g1.addEdge(0, 2);
  g1.addEdge(1, 2);
  g1.addEdge(2, 3);
  g1.printEulerTour();
 
  Graph g2(3);
  g2.addEdge(0, 1);
  g2.addEdge(1, 2);
  g2.addEdge(2, 0);
  g2.printEulerTour();
 
  Graph g3(5);
  g3.addEdge(1, 0);
  g3.addEdge(0, 2);
  g3.addEdge(2, 1);
  g3.addEdge(0, 3);
  g3.addEdge(3, 4);
  g3.addEdge(3, 2);
  g3.addEdge(3, 1);
  g3.addEdge(2, 4);
  g3.printEulerTour();
 
  return 0;
}