func_code_string: #include <bits/stdc++.h>   using namespace std;   long long int c = 0;   void bfs(map<long long int, vector<long long int> > &map, vector<bool> &visited,            long long int x) {     queue<long long int> q;     q.push(x);     visited[x] = true;     while (!q.empty()) {       long long int y = q.front();       q.pop();       for (long long int i : map[y]) {         if (!visited[i]) {           q.push(i);           visited[i] = true;         }       }     }   }   int main() {     long long int x, y, n, m;     cin >> n >> m;     map<long long int, vector<long long int> > map;     std::vector<bool> visited(n + 1, false), visitedf(n + 1, false);     for (long long int i = 0; i < m; i++) {       cin >> x >> y;       map[x].push_back(y);       map[y].push_back(x);     }     if (m != n - 1) {       cout <<  no ;       return 0;     }     bfs(map, visited, map.begin()->first);     for (long long int i = 1; i <= n; i++) {       if (!visited[i]) {         cout <<  no ;         return 0;       }     }     cout <<  yes ;   }   