T263133 拆网线

https://www.luogu.com.cn/record/85559526

Luogu/T263133/T263133.cpp

@@ -0,0 +1,69 @@
+#include <iostream>
+#include <cmath>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5;
+
+int t, n, k;
+std::vector<int> top, g[N];
+bool vis[N];
+
+void dfs(int u) {
+    vis[u] = true;
+
+    for (int v : g[u]) {
+        if (!vis[v]) dfs(v);
+    }
+
+    top.push_back(u);
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> t;
+
+    while (t--) {
+        top.clear();
+        std::fill_n(g, N, std::vector<int>());
+        std::fill_n(vis, N, false);
+
+        int ans = 0;
+
+        cin >> n >> k;
+
+        for (int i = 2, x; i <= n; i++) {
+            cin >> x;
+
+            g[i].push_back(x);
+            g[x].push_back(i);
+        }
+
+        dfs(1);
+
+        std::fill_n(vis, N, false);
+
+        for (int u : top) {
+            if (k <= 1) break;
+
+            if (vis[u]) continue;
+
+            for (int v : g[u]) {
+                if (vis[v]) continue;
+
+                vis[u] = vis[v] = true;
+                ans++;
+                k -= 2;
+            }
+        }
+
+        cout << ans + k << endl;
+    }
+
+    return 0;
+}