Create tarjan.cpp

tarjan.cpp

@@ -0,0 +1,41 @@
+constexpr int MAXN = 100'00;
+
+int n, m; // 0-based
+vector<int> graph[MAXN];
+///////////////////
+int dfsn[MAXN], scc[MAXN];
+stack<int> stk;
+vector<vector<int>> res;
+int ce;
+int dfs(int now)
+{
+    dfsn[now] = ce++;
+    int ret = dfsn[now];
+    stk.push(now);
+    for (int nxt: graph[now])
+    {
+        if (dfsn[nxt] == -1) ret = min(ret, dfs(nxt));
+        else if (scc[nxt] == -1) ret = min(ret, dfsn[nxt]);
+    }
+    if (ret == dfsn[now])
+    {
+        res.push_back(vector<int>());
+        int t;
+        do
+        {
+            t = stk.top(); stk.pop();
+            scc[t] = res.size() - 1;
+            res.back().push_back(t);
+        } while(t != now);
+    }
+    return ret;
+}
+void set_scc()
+{
+    memset(dfsn, -1, sizeof dfsn);
+    memset(scc, -1, sizeof scc);
+    res.clear();
+    ce = 0;
+    for (int i=0;i<n;++i)
+        if (dfsn[i] == -1) dfs(i);
+}