Cod sursa(job #869541)
#include <fstream>
#include <vector>
#include <list>
using namespace std;
ifstream f("biconex.in");
ofstream g("biconex.out");
int n,d[100001],low[100001],c=0;
vector <int> v[100001],sol[100001];
list < pair<int, int> > stiva;
void empty(int x,int y)
{
while(stiva.front().first!=x && stiva.front().second!=y)
{
sol[c].push_back(stiva.front().second);
stiva.pop_front();
}
sol[c].push_back(x);
sol[c].push_back(y);
stiva.pop_front();
}
void dfs(int x, int t)
{
int i,y;
d[x]=d[t]+1;
low[x]=d[x];
for(i=0;i<v[x].size();i++)
{
y=v[x][i];
if(y!=t)
{
if(!d[y])
{
stiva.push_front(make_pair(x,y));
dfs(y,x);
if(low[y]>=d[x]) {c++; empty(x,y);}
}
if(low[y]<low[x]) low[x]=low[y];
}
}
}
int main()
{
int i,j,m,x,y;
f>>n>>m;
for(i=1;i<=m;i++)
{
f>>x>>y;
v[x].push_back(y);
v[y].push_back(x);
}
stiva.push_back(make_pair(1,0));
dfs(1,0);
g<<c<<'\n';
for(i=1;i<=c;i++)
{
for(j=0;j<sol[i].size();j++)
g<<sol[i][j]<<' ';
g<<'\n';
}
}