python/TangDou/Topic/HuanGenDp/CF1187E.cpp

#include <bits/stdc++.h>
using namespace std;
const int N = 200010;
#define int long long
#define endl "\n"

vector<int> son[N];
int vis[N], n;
int sz[N];
int f[N];
void dfs(int u) {
    sz[u] = 1;
    vis[u] = 1;
    for (int i = 0; i < son[u].size(); i++) {
        int v = son[u][i];
        if (!vis[v]) {
            dfs(v);
            sz[u] += sz[v];
        }
    }
}
void dp(int u) {
    vis[u] = 1;
    for (int i = 0; i < son[u].size(); i++) {
        int v = son[u][i];
        if (!vis[v]) {
            f[v] = f[u] + sz[1] - 2 * sz[v];
            dp(v);
        }
    }
}

signed main() {
    cin >> n;
    for (int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        son[u].push_back(v);
        son[v].push_back(u);
    }
    dfs(1);

    for (int i = 1; i <= n; i++) f[1] += sz[i];

    memset(vis, 0, sizeof(vis));
    dp(1);

    int ans = -0x3f;
    for (int i = 1; i <= n; i++) ans = max(ans, f[i]);

    cout << ans << endl;
}