106. Точки сочленения

#include <bits/stdc++.h>

using namespace std;

int n,m;
vector<vector<int> > g;
vector<int> tin,fup;
vector<char> used;
int timer=0;

vector<int> c;

void is_cutpoint(int v) {
    c.push_back(v);
}

void dfs(int v,int p=-1) {
    used[v]=true;
    tin[v]=fup[v]=timer++;
    int children=0;
    for (int i=0;i<(int)g[v].size();++i) {
        int to=g[v][i];
        if (to==p) continue;
        if (used[to]) {
            fup[v]=min(fup[v],tin[to]);
        } else {
            dfs(to,v);
            fup[v]=min(fup[v],fup[to]);
            if (fup[to]>=tin[v] && p!=-1)
                is_cutpoint(v);
            ++children;
        }
    }
    if (p==-1 && children>1)
        is_cutpoint(v);
}

int main(int argc, char **argv)
{
    cin >> n >> m;
    g.resize(n);
    used.resize(n,false);
    tin.resize(n),fup.resize(n);
    for (int i=0;i<m;++i) {
        int u,v;
        cin >> u >> v;
        --u,--v;
        g[u].push_back(v);
        g[v].push_back(u);
    }

    dfs(0);

    sort(c.begin(),c.end());

    cout << (int)c.size() << endl;
    for (int i=0;i<(int)c.size();++i)
        cout << c[i]+1 << " ";

    return 0;
}