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// Laufzeit: O(|V|+|E|)
vector<vector<int>> adjlist;
vector<bool> isArt;
vector<int> d, low;
int counter, root, rootCount; // rootCount >= 2 <=> root Artikulationspunkt
vector<ii> bridges; // Nur fuer Brücken.
void dfs(int v, int parent = -1) {
d[v] = low[v] = ++counter;
if (parent == root) ++rootCount;
for (auto w : adjlist[v]) {
if (!d[w]) {
dfs(w, v);
if (low[w] >= d[v] && v != root) isArt[v] = true;
if (low[w] > d[v]) bridges.push_back(ii(v, w));
low[v] = min(low[v], low[w]);
} else if (w != parent) {
low[v] = min(low[v], d[w]);
}}}
void findArticulationPoints() {
counter = 0;
low.resize(adjlist.size());
d.assign(adjlist.size(), 0);
isArt.assign(adjlist.size(), false);
bridges.clear(); //nur fuer Bruecken
for (int v = 0; v < (int)adjlist.size(); v++) {
if (!d[v]) {
root = v; rootCount = 0;
dfs(v);
if (rootCount > 1) isArt[v] = true;
}}}
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