Add articulation point algorithm

Author: Madhur215

Data Structures/Graphs/Articulation_Point.cpp

@@ -0,0 +1,74 @@
+#include <bits/stdc++.h>
+#define fastio ios_base::sync_with_stdio(false);cin.tie(NULL);cout<<fixed;cout.precision(10);
+#define endl "\n"
+#define tc ll T; cin >> T; while(T--)
+#define pb push_back
+#define mod 1000000007
+#define S second
+#define F first
+using namespace std;
+typedef long long ll;
+const int N = 1e4+5;
+
+int n, m, inTm, ans;
+vector<int> adj[N], vis(N);
+vector<int> low(N), par(N), inTime(N), ap(N);
+
+void articulationP(int s){
+
+ int cnt = 0;
+ vis[s] = 1;
+ inTime[s] = low[s] = ++inTm;
+
+ for(auto i : adj[s]){
+
+ if(!vis[i]){
+ cnt++;
+ par[i] = s;
+ articulationP(i);
+ low[s] = min(low[s], low[i]);
+
+ if(par[s] == -1 and cnt > 1) ap[s] = 1;
+ if(par[s] != -1 and low[i] >= inTime[s]) ap[s] = 1;
+ }
+ else if(i != par[s]) low[s] = min(low[s], inTime[i]);
+ }
+
+}
+
+int main(){
+ 
+ fastio;
+ while(1){
+ cin >> n >> m;
+ if(n == 0 and m == 0) break;
+ int a, b; 
+ ans = inTm = 0;
+ vis.clear(); vis.resize(N);
+ low.clear(); low.resize(N);
+ par.clear(); par.resize(N, -1);
+ ap.clear(); ap.resize(N);
+ inTime.clear(); inTime.resize(N);
+ for(int i = 0; i < N; i++) adj[i].clear();
+
+ for(int i = 0; i < m; i++){
+ cin >> a >> b;
+ adj[a].pb(b);
+ adj[b].pb(a);
+ }
+ for(int i = 1; i <= n; i++){
+ if(!vis[i]){
+ articulationP(i);
+ }
+ }
+ 
+ for(int i = 1; i <= n; i++)
+ ans += ap[i];
+ cout << ans << endl;
+
+
+ }
+
+ return 0;
+ 
+}