Distances

#include <bits/stdc++.h>
 
using namespace std;
 
#define f first
#define s second
 
typedef long long ll;
typedef pair<int,int> pi;
 
vector<int> edges[101];
 
//even first time, odd after
void dfs(int node, int p, int d){
    if((d&1) == 0) cout << node << " ";
    for(auto &a: edges[node]){
        if(a == p) continue;
        dfs(a, node, d+1);
    }
    if(d&1) cout << node << " ";
}
 
int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
    int t; cin >> t;
    while(t--){
        int n; cin >> n;
        for(int i = 1; i <= n; i++) edges[i].clear();
        for(int i = 1; i < n; i++){
            int u,v; cin >> u >> v;
            edges[u].push_back(v);
            edges[v].push_back(u);
        }
        dfs(1,0,0);
        cout << "\n";
    }
    return 0;
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED