python/TangDou/Topic/HuanGenDp/CF1187E.cpp

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

const int N = 200010, M = N << 1;

int n;

// 链式前向星
int e[M], h[N], idx, w[M], ne[M];
void add(int a, int b, int c = 0) {
    e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
}

int sz[N], f[N], g[N], ans;

void dfs1(int u, int fa) {
    sz[u] = 1;
    for (int i = h[u]; ~i; i = ne[i]) {
        int v = e[i];
        if (v == fa) continue;
        dfs1(v, u);
        sz[u] += sz[v];
        f[u] += f[v];
    }
    f[u] += sz[u];
}
void dfs2(int u, int fa) {
    for (int i = h[u]; ~i; i = ne[i]) {
        int v = e[i];
        if (v == fa) continue;
        g[v] = n - sz[v] + g[u] - sz[v];
        dfs2(v, u);
    }
}

signed main() {
    // 初始化链式前向星
    memset(h, -1, sizeof h);

    cin >> n;
    for (int i = 1; i < n; i++) {
        int a, b;
        cin >> a >> b;
        add(a, b), add(b, a);
    }
    dfs1(1, 0);
    g[1] = f[1];
    dfs2(1, 0);
    int ans = 0;
    for (int i = 1; i <= n; i++) ans = max(ans, g[i]);
    cout << ans << endl;
}