P3388 【模板】割点（割顶）

P3388 【模板】割点（割顶）

Luogu/P3388/P3388.cpp

@@ -0,0 +1,62 @@
+#include <iostream>
+#include <vector>
+
+using std::cin;
+using std::cout;
+using std::endl;
+
+const int N = 20005;
+
+int n, m, x, y;
+std::vector<int> ans, g[N];
+
+// Tarjan
+int cnt, dfn[N], low[N];
+int root;
+bool cut[N];
+
+void tarjan(int u) {
+    dfn[u] = low[u] = ++cnt;
+    bool flag = false;
+    for (int v : g[u]) {
+        if (!dfn[v]) {
+            tarjan(v);
+            low[u] = std::min(low[u], low[v]);
+            if (dfn[u] <= low[v]) {
+                if (u != root || flag) {
+                    cut[u] = true;
+                } else {
+                    flag = true;
+                }
+            }
+        } else {
+            low[u] = std::min(low[u], dfn[v]);
+        }
+    }
+}
+
+int main() {
+    cin >> n >> m;
+    for (int i = 1; i <= m; i++) {
+        cin >> x >> y;
+        g[x].push_back(y);
+        g[y].push_back(x);
+    }
+    for (int i = 1; i <= n; i++) {
+        if (!dfn[i]) {
+            root = i;
+            tarjan(i);
+        }
+    }
+    for (int i = 1; i <= n; i++) {
+        if (cut[i]) {
+            ans.push_back(i);
+        }
+    }
+    cout << ans.size() << endl;
+    for (int i : ans) {
+        cout << i << ' ';
+    }
+    cout << endl;
+    return 0;
+}