Distances

#include <bits/stdc++.h>
using namespace std;

#define pb push_back
#define fr first
#define sc second
#define clr(a, x) memset(a, x, sizeof(a))
#define dbg(x) cout<<"("<<#x<<"): "<<x<<endl;
#define printvector(arr) for (auto it = arr.begin(); it != arr.end(); ++it) cout<<*it<<" "; cout<<endl;
#define all(v) v.begin(), v.end()
#define lcm(a, b) (a * b)/__gcd(a, b)
#define int long long int
#define printvecpairs(vec) for(auto it: vec) cout<<it.fr<<' '<<it.sc<<endl;
#define endl '\n'
#define float long double

const int MOD = 1e9 + 7;
const int INF = 2e15;
const int MAXN = 1e5 + 5;

vector<int> adj[MAXN];
vector<int> ans;

void dfs(int u, int p, int put){
    if(put) ans.push_back(u);
    for(int v: adj[u]){
        if(v==p) continue;
        dfs(v, u, 1-put);
    }
    if(!put) ans.push_back(u);
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    #ifdef LOCAL
    freopen("input.txt", "r", stdin);
    #endif
    int t;
    cin>>t;
    while(t--){
    	int n;
    	cin>>n;
        ans.clear();
    	for(int i= 0;i<=n+1;i++){
    		adj[i].clear();
    	}
    	for(int i= 0;i<n-1;i++){
    		int t1, t2;
    		cin>>t1>>t2;
    		adj[t1].pb(t2);
    		adj[t2].pb(t1);
    	}
        dfs(1, -1, 1);
        printvector(ans);
    }

    return 0;
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED