#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <unordered_set>
#include <stack>

//std::ifstream f("graful.txt");
//std::ofstream g("graful.out");
std::ifstream f("biconex.in");
std::ofstream g("biconex.out");

// Obs: graful initial este conex
int start = 0, contor;   // contorul il vom folosi in mai multe probleme;  start va aparea eventual ca nod de start

typedef std::stack< std::pair <int, int > > stackpair;
typedef std::unordered_set< int > multime;
typedef std::vector< std::vector < int > > vector_vectori;

class graf
{
	int nrvf, nrmuchii;
	std::vector<int>* vecini;

public:
	graf(bool orientat);

	void verifvecini();

	void BFS();
	void DFS(int nod, bool* viz);
	void cadruDFS();
	void biconexe(int nod, int tata, bool* viz, multime* wayback, stackpair& muchiiviz, vector_vectori& comp_biconexe);
	void cadru_biconexe();

	~graf()
	{
		delete []vecini;
	}
};

graf::graf(bool orientat)
{
	f >> nrvf >> nrmuchii;
	if(start == 1)	// daca avem de citit un nod de start...
		f >> start;

	vecini = new std::vector<int>[nrvf + 1];
	if (orientat == true)
		for (int i = 0; i < nrmuchii; i++)
		{
			int x, y;
			f >> x >> y;
			vecini[x].push_back(y);
		}
	else
		for (int i = 0; i < nrmuchii; i++)
		{
			int x, y;
			f >> x >> y;
			vecini[x].push_back(y);
			vecini[y].push_back(x);
		}
}

void graf::verifvecini()
{
	for (int i = 1; i <= nrvf; i++)
	{
		std::cout << "\n  vecinii lui " << i << " :  ";
		for (unsigned int j = 0; j < vecini[i].size(); j++)
			std::cout << vecini[i][j] << " ";
	}
}

void graf::BFS()
{
	int* dist = new int[nrvf + 1]{ 0 };	// initializam distantele cu 0 (le decrementam ulterior)
	std::queue <int> qBFS;	  // coada pt BFS
	qBFS.push(start);
	dist[start] = 1;

	while (!qBFS.empty())
	{
		const int nod = qBFS.front();
		for (unsigned int i = 0; i < vecini[nod].size(); i++)
		{
			const int nod_urm = vecini[nod][i];
			if (dist[nod_urm] == 0)
			{
				qBFS.push(nod_urm);
				dist[nod_urm] = dist[nod] + 1;
			}
		}

		qBFS.pop();
	}

	for (int i = 1; i <= nrvf; i++)
		g << dist[i] - 1 << " ";

	delete [] dist;
}

void graf::DFS(int nod, bool* viz)
{
	viz[nod] = true;
	for (unsigned int i = 0; i < vecini[nod].size(); i++)
	{
		const int nod_urm = vecini[nod][i];
		if (!viz[nod_urm])
			DFS(nod_urm, viz);
	}
}

void graf::cadruDFS()
{
	contor = 0;
	bool* viz = new bool[nrvf + 1]{ 0 };
	for (int i = 1; i <= nrvf; i++)
		if( ! viz[i] )
		{
			contor++;
			DFS(i, viz);
		}
	g << contor;
	delete[]viz;
}

void graf::biconexe(int nod, int tata, bool* viz, multime* wayback, stackpair& muchiiviz, vector_vectori& comp_biconexe)
{
	viz[nod] = true;

	for (unsigned int i = 0; i < vecini[nod].size(); i++)
	{
		const int nod_urm = vecini[nod][i];

		if (viz[nod_urm]) 
		{
			if (nod_urm != tata and nod_urm != nod) 
			{
				wayback->insert(nod_urm);
				for(unsigned int i = 0; i < vecini[nod_urm].size(); i ++ )
					if (vecini[nod_urm][i] == nod)
					{
						vecini[nod_urm][i] = nod_urm;
						break;
					}
			}
		}
		else
		{
			muchiiviz.push({ nod, nod_urm });
			multime* wayback_fiu = new multime;
			biconexe(nod_urm, nod, viz, wayback_fiu, muchiiviz, comp_biconexe);
			
			wayback_fiu->erase(nod);
			if (wayback_fiu->size() == 0)
			{
				contor++;
				std::vector< int > aux;
				comp_biconexe.push_back(aux);
				while (muchiiviz.top().first != nod)
				{
					comp_biconexe.back().push_back(muchiiviz.top().second);
					muchiiviz.pop();
				}
				comp_biconexe.back().push_back(muchiiviz.top().second);
				comp_biconexe.back().push_back(muchiiviz.top().first);
				muchiiviz.pop();
			}
			else
				wayback->insert(wayback_fiu->begin(), wayback_fiu->end());

			delete wayback_fiu;
		}
	}
	
}

void graf::cadru_biconexe()
{
	contor = 0;
	vector_vectori comp_biconexe;		// solutia, de forma unui vector cu alti vectori ce reprezinta componentele biconexe
	bool* viz = new bool[nrvf + 1]{ 0 };	// nodurile vizitate deja
	stackpair muchiiviz;							// stiva de muchii vizitate
	multime* setgol = new multime;		// un set "wayback" pe care il pasez fiului pentru a-mi returna caile de intoarcere disponibile
	biconexe(1, -1, viz, setgol, muchiiviz, comp_biconexe);
	delete setgol;

	g << contor << "\n";
	for (unsigned int i = 0; i < comp_biconexe.size(); i++)
	{
		for (unsigned int j = 0; j < comp_biconexe[i].size(); j++) {
			g << comp_biconexe[i][j] << " ";
		}
		g << "\n";
	}
}

int main()
{
	start = 0;		// afirmam daca citim si un nod de start;
	graf g(false);
	g.cadru_biconexe();

	return 0;
}