P3388 【模板】割点（割顶）

https://www.luogu.com.cn/record/91855549

Luogu/P3388/P3388.cpp

@@ -1,23 +1,22 @@
 #include <iostream>
+#include <algorithm>
 #include <vector>
 
 using std::cin;
 using std::cout;
-using std::endl;
+const char endl = '\n';
 
-const int N = 20005;
+const int N = 2e4 + 5;
 
-int n, m, x, y;
+int n, m;
-std::vector<int> ans, g[N];
+std::vector<int> g[N];
-
+int root, cnt, dfn[N], low[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);
@@ -36,27 +35,34 @@ void tarjan(int u) {
 }
 
 int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
     cin >> n >> m;
-    for (int i = 1; i <= m; i++) {
+
+    for (int i = 1, x, y; i <= m; i++) {
         cin >> x >> y;
-        g[x].push_back(y);
+
-        g[y].push_back(x);
+        g[x].emplace_back(y);
+        g[y].emplace_back(x);
     }
+
     for (int i = 1; i <= n; i++) {
         if (!dfn[i]) {
             root = i;
             tarjan(i);
         }
     }
+
+    cout << std::count(cut + 1, cut + n + 1, true) << endl;
+
     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;
 }