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Articulation Points.cpp
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Articulation Points.cpp
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const int N = 1e5 + 5;
int n;
int timer;
int tin[N], low[N];
bool vis[N], isArticulation[N];
vector<int> g[N];
void dfs(int u, int par)
{
vis[u] = 1;
tin[u] = low[u] = ++timer;
int children = 0;
for(auto &it:g[u])
{
if(it == par)
continue;
if(vis[it])
low[u] = min(low[u], tin[it]);
else
{
dfs(it, u);
low[u] = min(low[u], low[it]);
if(low[it] >= tin[u] && par != -1)
isArticulation[u] = 1;
children++;
}
}
if(par == -1 && children > 1)
isArticulation[u] = 1;
}
void articulationPoints()
{
timer = 0;
memset(vis, 0, sizeof(vis));
memset(isArticulation, 0, sizeof(isArticulation));
memset(tin, -1, sizeof(tin));
memset(low, -1, sizeof(low));
for(int i = 1; i <= n; i++)
{
if(!vis[i])
dfs(i, -1);
}
}