func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long int sz = 2e5;   long long int col[sz], vis[sz];   vector<long long int> adj[sz];   long long int n;   void reset() {     long long int i;     for (i = 0; i < n + 14; i++) {       col[i] = -1;       adj[i].clear();       vis[i] = 0;     }   }   void coloring(long long int n, long long int c) {     vis[n] = 1;     col[n] = c;     for (auto it : adj[n]) {       if (vis[it] == 0) coloring(it, c ^ 1);     }   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     ;     long long int i, j, k, len, x, y, z, c, f, flag, p, q, mx, mn, l, r, sum, ans,         tmp, it, pos, avg, m, cnt;     long long int t;     cin >> t;     while (t--) {       f = 0;       flag = 0;       ans = 0;       cnt = 0;       sum = 0;       mn = LLONG_MAX;       mx = LLONG_MIN;       string s;       cin >> n >> m;       reset();       for (i = 0; i < m; i++) {         cin >> l >> r;         adj[l].push_back(r);         adj[r].push_back(l);       }       coloring(1, 0);       vector<long long int> sol1, sol2;       for (i = 1; i <= n; i++) {         if (col[i])           sol1.push_back(i);         else           sol2.push_back(i);       }       if (sol2.size() < sol1.size()) {         cout << sol2.size() <<   n ;         for (auto dsp : sol2) cout << dsp <<    ;         cout <<   n ;         ;       } else {         cout << sol1.size() <<   n ;         for (auto dsp : sol1) cout << dsp <<    ;         cout <<   n ;         ;       }     }     return 0;   }   