Distances

#pragma GCC optimize("O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx")
#include <bits/stdc++.h>
 
using namespace std;
 
using ll = long long;
using ld = long double;
 
const int mod = 1e9 + 7;
 
ll binpow(ll a, ll p) {
    ll res = 1;
    while (p) {
        if (p & 1) {
            (res *= a) %= mod;
        }
        p >>= 1;
        (a *= a) %= mod;
    }
    return res;
}

void solve() {
    int n;
    cin >> n;
    vector<vector<int>> g(n + 1);
    for (int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }

    vector<int> order;
    vector<int> used(n + 1);
    function<void(int)> dfs = [&](int v) {
        if (used[v] == 1) {
            order.push_back(v);
        }
        for (int u : g[v]) {
            if (!used[u]) {
                used[u] = 3 - used[v];
                dfs(u);
            }
        }
        if (used[v] == 2) {
            order.push_back(v);
        }
    };

    used[1] = 1;
    dfs(1);
    for (int v : order) {
        cout << v << ' ';
    }
    cout << '\n';
}
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int T = 1;
    cin >> T;
    for (int tc = 1; tc <= T; tc++) {
        // cout << "Case #" << tc << ": ";
        solve();
    }
    return 0;
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED