func_code_string: #include <bits/stdc++.h>   using namespace std;   int t;   vector<vector<int> > nod;   vector<int> sol;   void bfs(int n) {     sol = vector<int>(n + 10);     sol[1] = 1;     queue<int> Q;     Q.push(1);     while (!Q.empty()) {       int a = Q.front();       Q.pop();       for (int j = 0; j < nod[a].size(); j++)         if (!sol[nod[a][j]]) {           sol[nod[a][j]] = sol[a] + 1;           Q.push(nod[a][j]);         }     }   }   int main() {     cin >> t;     while (t--) {       int n, m;       cin >> n >> m;       nod = vector<vector<int> >(n + 5);       for (int i = 1; i <= m; i++) {         int nod1, nod2;         cin >> nod1 >> nod2;         nod[nod1].push_back(nod2);         nod[nod2].push_back(nod1);       }       bfs(n);       vector<int> nr1, nr2;       for (int i = 1; i <= n; i++) {         if (sol[i] & 1)           nr1.push_back(i);         else           nr2.push_back(i);       }       if (nr1.size() < nr2.size()) {         cout << nr1.size() <<   n ;         for (int i = 0; i < nr1.size(); i++) cout << nr1[i] <<    ;         cout <<   n ;       } else {         cout << nr2.size() <<   n ;         for (int i = 0; i < nr2.size(); i++) cout << nr2[i] <<    ;         cout <<   n ;       }     }     return 0;   }   