func_code_string: #include <bits/stdc++.h>   using namespace std;   vector<int> a[2000007];   vector<int> deg(2000007, 0);   vector<pair<int, int>> ans;   int n, m;   void bfs(int node) {     vector<bool> used(n);     used[node] = true;     queue<int> q;     q.push(node);     while (!q.empty()) {       int currnode = q.front();       q.pop();       for (auto x : a[currnode]) {         if (used[x]) continue;         ans.push_back({x, currnode});         used[x] = true;         q.push(x);       }     }   }   void solve() {     cin >> n >> m;     int u, v;     for (int i = 0; i < m; i++) {       cin >> u >> v;       u--;       v--;       a[u].push_back(v);       a[v].push_back(u);       deg[u]++;       deg[v]++;     }     int maxnode = 0;     for (int i = 0; i < n; i++) {       if (deg[maxnode] < deg[i]) maxnode = i;     }     bfs(maxnode);     for (auto x : ans) {       cout << x.first + 1 <<     << x.second + 1 << endl;     }   }   int main() {     int t;     t = 1;     while (t--) solve();     return 0;   }   