Language: C++

#include <bits/stdc++.h>
using namespace std;

int main(){
  int n,m;
  cin>>n>>m;
  vector<vector<int>> info(m,vector<int>(2));
  vector<int> index(m);
  for(int i=0;i<m;i++){
    cin>>info.at(i).at(0)>>info.at(i).at(1);
    index.at(i)=i;
  }
  set<int> friends;
  bool next;
  int m=1;
  int sum=0;
  while(index.size()>0){
    next=false;
    friends={info.at(index.at(0)).at(0),info.at(index.at(0)).at(1)};
    index.erase(index.begin());
    while(!next){
      next=true;
      for(int i=(int)index.size()-1;i>=0;i--){
        if(friends.count(info.at(index.at(i)).at(0))){
          friends.insert(info.at(index.at(i)).at(1));
          index.erase(index.begin()+i);
          next=false;
        }else if(friends.count(info.at(index.at(i)).at(1))){
          friends.insert(info.at(index.at(i)).at(0));
          index.erase(index.begin()+i);
          next=false;
        }
      }
      /*
      for(int i=0;i<(int)index.size();i++){
        if(friends.count(info.at(index.at(i)).at(0))){
          friends.insert(info.at(index.at(i)).at(1));
          index.erase(index.begin()+i);
          i--;
          next=false;
        }else if(friends.count(info.at(index.at(i)).at(1))){
          friends.insert(info.at(index.at(i)).at(0));
          index.erase(index.begin()+i);
          i--;
          next=false;
        }
      }
      */
    }
    sum+=friends.size();
    m=max(m,friends.size());
    if(n-sum<=m){
      break;
    }
  }
  cout<<m<<endl;
}
      
                       
                       
  







Compiler output:
a.cc: In function 'int main()':
a.cc:15:7: error: redeclaration of 'int m'
   15 |   int m=1;
      |       ^
a.cc:5:9: note: 'int m' previously declared here
    5 |   int n,m;
      |         ^
a.cc:51:10: error: no matching function for call to 'max(int&, std::set<int>::size_type)'
   51 |     m=max(m,friends.size());
      |       ~~~^~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:51:10: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'std::set<int>::size_type' {aka 'long unsigned int'})
   51 |     m=max(m,friends.size());
      |       ~~~^~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:51:10: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   51 |     m=max(m,friends.size());
      |       ~~~^~~~~~~~~~~~~~~~~~