Tree cutting

#include <bits/stdc++.h>
const int N = 1e5 + 10, M = 2 * N, mod = 1e9 + 7;
using namespace std;
int h[N], e[M], ne[M], idx = 0;
int n, s, siz[N];
bool st[N];
void add(int x, int y){
    e[idx] = y, ne[idx] = h[x], h[x] = idx ++;
}
void dfs(int u, int fa){
    siz[u] = 1;
    for(int i = h[u]; i != -1; i = ne[i]){
        int j = e[i];
        if(j == fa) continue;
        dfs(j, u);
        if(siz[j] > n / 2) st[u] = false;
        siz[u] += siz[j];
    }
    if(n - siz[u] > n / 2) st[u] = false;
}
int main()
{
    memset(h, -1, sizeof h);
    memset(st, true, sizeof st);
    cin >> n;
    for(int i = 1; i < n; i ++){
        int x, y;
        cin >> x >> y;
        add(x, y), add(y, x);
    }
    dfs(1, -1);
    bool flag = true;
    for(int i = 1; i <= n; i ++){
        if(st[i]){
            cout << i << endl;
            flag = false;
        }
    }
    if(flag){
        puts("NONE");
    }
    return 0;
}
/*
3 100
1 2 3
1 2
2 3
*/