func_code_string: #include <bits/stdc++.h>   using namespace std;   vector<int> e[100500];   bool visited[100500];   int main() {     int n, m;     scanf( %d%d , &n, &m);     if (m != n - 1) {       cout <<  no  << endl;       return 0;     }     for (int i = 0; i < m; i++) {       int u, v;       scanf( %d%d , &u, &v);       u--;       v--;       e[u].push_back(v);       e[v].push_back(u);     }     visited[0] = true;     list<int> sp;     sp.push_back(0);     while (sp.begin() != sp.end()) {       int u = sp.front();       sp.pop_front();       for (int i = 0; i < e[u].size(); i++) {         int v = e[u][i];         if (!visited[v]) sp.push_back(v);         visited[v] = true;       }     }     for (int i = 0; i < n; i++)       if (!visited[i]) {         cout <<  no  << endl;         return 0;       }     cout <<  yes  << endl;     return 0;   }   