846. 树的重心

https://www.acwing.com/problem/content/submission/code_detail/13140613/

AcWing/846/846.cpp

@@ -0,0 +1,46 @@
+#include <iostream>
+#include <limits>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 100005;
+
+int n, ans = std::numeric_limits<int>::max();
+std::vector<int> g[N];
+
+int dfs(int u, int fa) {
+    int siz = 0, sum = 0;
+
+    for (int v : g[u]) {
+        if (v != fa) {
+            int s = dfs(v, u);
+            siz = std::max(siz, s);
+            sum += s;
+        }
+    }
+
+    ans = std::min(ans, std::max(siz, n - sum - 1));
+
+    return sum + 1;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> n;
+    for (int i = 1, u, v; i < n; i++) {
+        cin >> u >> v;
+
+        g[u].push_back(v);
+        g[v].push_back(u);
+    }
+
+    dfs(1, -1);
+
+    cout << ans << endl;
+
+    return 0;
+}