Language: C++

#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef long double lld;
ll MOD = (1e9)+7;
const int dr[] = {+1, -1, +0, +0, +1, -1, +1, -1};
const int dc[] = {+0, +0, +1, -1, +1, -1, -1, +1};
const int kx[] = {+1, +2, -1, -2, +1, +2, -1, -2};
const int ky[] = {+2, +1, +2, +1, -2, -1, -2, -1};
//#pragma GCC target ("avx2")
//#pragma GCC optimization ("O3")
//#pragma GCC optimization ("unroll-loops")
inline void fastIO(){
  ios_base::sync_with_stdio(0);cin.tie(0);
}
template<typename T> ostream& operator<<(ostream &os, const vector<T> &v) { os << '{'; string sep; for (const auto &x : v) os << sep << x, sep = ", "; return os << '}'; }
template<typename T, size_t size> ostream& operator<<(ostream &os, const array<T, size> &arr) { os << '{'; string sep; for (const auto &x : arr) os << sep << x, sep = ", "; return os << '}'; }
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }

void debug_out() { cerr << endl; }
template<typename Head, typename... Tail> void debug_out(Head H, Tail... T) { cerr << ' ' << H; debug_out(T...); }

#ifdef LOCAL
#define debug(...) cerr << "(" << #__VA_ARGS__ << "):", debug_out(__VA_ARGS__)
#else
#define debug(...) 47
#endif

int n,m,size=0,ans=0;
vector<vector<int>>adj(202020);
vector<bool>vis(202020,false);
void DFS(int source){
  vis[source]=true;
  for(auto node:adj[source]){
    if(!vis[node]){
      size++;
      DFS(node);
    }
  }
}
int main(){
  fastIO();
  cin>>n>>m;
  for(int i=0;i<m;i++){
    int nodeA,nodeB;
    cin>>nodeA>>nodeB;
    adj[nodeA].push_back(nodeB);
    adj[nodeB].push_back(nodeA);
  }
  for(int i=1;i<=n;i++){
    if(!vis[i]){
      size=0;
      DFS(i);
      ans=max(ans,size);
    }
  }
  cout<<ans+1<<endl;
  return 0;
}


Compiler output:
a.cc: In function 'void DFS(int)':
a.cc:36:7: error: reference to 'size' is ambiguous
   36 |       size++;
      |       ^~~~
In file included from /usr/include/c++/14/string:53,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52,
                 from a.cc:1:
/usr/include/c++/14/bits/range_access.h:272:5: note: candidates are: 'template<class _Tp, long unsigned int _Nm> constexpr std::size_t std::size(const _Tp (&)[_Nm])'
  272 |     size(const _Tp (&)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:262:5: note:                 'template<class _Container> constexpr decltype (__cont.size()) std::size(const _Container&)'
  262 |     size(const _Container& __cont) noexcept(noexcept(__cont.size()))
      |     ^~~~
a.cc:29:9: note:                 'int size'
   29 | int n,m,size=0,ans=0;
      |         ^~~~
a.cc: In function 'int main()':
a.cc:52:7: error: reference to 'size' is ambiguous
   52 |       size=0;
      |       ^~~~
/usr/include/c++/14/bits/range_access.h:272:5: note: candidates are: 'template<class _Tp, long unsigned int _Nm> constexpr std::size_t std::size(const _Tp (&)[_Nm])'
  272 |     size(const _Tp (&)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:262:5: note:                 'template<class _Container> constexpr decltype (__cont.size()) std::size(const _Container&)'
  262 |     size(const _Container& __cont) noexcept(noexcept(__cont.size()))
      |     ^~~~
a.cc:29:9: note:                 'int size'
   29 | int n,m,size=0,ans=0;
      |         ^~~~
a.cc:54:19: error: reference to 'size' is ambiguous
   54 |       ans=max(ans,size);
      |                   ^~~~
/usr/include/c++/14/bits/range_access.h:272:5: note: candidates are: 'template<class _Tp, long unsigned int _Nm> constexpr std::size_t std::size(const _Tp (&)[_Nm])'
  272 |     size(const _Tp (&)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:262:5: note:                 'template<class _Container> constexpr decltype (__cont.size()) std::size(const _Container&)'
  262 |     size(const _Container& __cont) noexcept(noexcept(__cont.size()))
      |     ^~~~
a.cc:29:9: note:                 'int size'
   29 | int n,m,size=0,ans=0;
      |         ^~~~