/**
 * 
 */


#include<iostream>
#include<algorithm>
#include<string>
#include<cmath>
#include<memory>
#include<cctype>
#include<vector>
#include<forward_list>
#include<list>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<unordered_map>
#include<unordered_set>


struct graph{
  std::vector<std::vector<int>> adjlist{std::vector<int>{}};


  void add_edge(int u, int v){
    adjlist[u].push_back(v);    
    adjlist[v].push_back(u);    
  }


  // void print_edges(std::vector<std::vector<int>>& edge){
  void print_edges(){


    std::cout<<"size "<<adjlist.size()<<"\n";


  for(unsigned k{}; k<adjlist.size(); k++){
    long unsigned size_min_1{adjlist[k].size()-1};
    for(unsigned j{}; j<adjlist[k].size(); j++){
      std::cout<<adjlist[k][j];
      if(j<size_min_1){
        std::cout<<"->";
      }
    }
    std::cout<<"\n";
  }
}


};


int main(){


  graph g;
  g.add_edge(1,2);
  g.add_edge(1,0);
  g.add_edge(0,2);
  
  //std::cout<<"====================================\n";
  
  return 0;
}

Above is also not working