new file: CF1187E.cpp

CF1187E.cpp

@@ -0,0 +1,45 @@
+#include<bits/stdc++.h>
+#define int long long
+using namespace std;
+int n;
+vector<int> fri[200005];
+int siz[200005];
+int f[200005];
+int ans[200005];
+void dfs(int now, int from) {
+    siz[now] = 1;
+    f[now] = 0;
+    for(int i:fri[now]) {
+        if(i == from) continue;
+        dfs(i, now);
+        f[now] += f[i];
+        siz[now] += siz[i];
+    }
+    f[now] += siz[now];
+}
+void pass(int now, int from) {
+    for(int i:fri[now]) {
+        if(i == from) continue;
+        ans[i] = ans[now] + n - siz[i] * 2;
+        pass(i, now);
+    }
+}
+signed main() {
+    scanf("%lld", &n);
+    for(int i = 1, u, v; i < n; ++i) {
+        scanf("%lld%lld", &u, &v);
+        fri[u].push_back(v);
+        fri[v].push_back(u);
+    }
+    dfs(1, -1);
+    ans[1] = f[1];
+    pass(1, -1);
+    int res = ans[1];
+    for(int i = 1; i <= n; ++i) res = max(res, ans[i]);
+    printf("%lld\n", res);
+    return 0;
+}
+/*
+dp[i] 表示 i 子树中将 i 先染色的最大贡献
+g u=g father u+n−siz u×2
+*/