Create tarjan_scc.cpp

Graph/tarjan_scc.cpp

@@ -0,0 +1,27 @@
+int cnt, scc_num, scc[MAXN], in[MAXN], low[MAXN];
+stack<int> s;
+bitset<MAXN> ins;
+
+void tarjan(int u) {
+	low[u] = in[u] = cnt++;
+	s.push(u);
+	ins[u] = 1;
+	for (int v : G[u]) {
+		if (in[v] == -1) tarjan(v), low[u] = min(low[u], low[v]);
+		else if (ins[v]) low[u] = min(low[u], in[v]);
+	}
+	if (low[u] == in[u]) {
+		while (1) {
+			int x = s.top(); s.pop();
+			scc[x] = scc_num, ins[x] = 0;
+			if (x == u) break;
+		}
+		++scc_num;
+	}
+}
+
+
+memset(scc, -1, sizeof scc), memset(in, -1, sizeof in);
+for (int u = 1; u <= N; u++) {
+	if (scc[u] == -1) tarjan(u);
+}