Language: C++

                              //          ★★ ASHWINI SHARMA ★★ 
#include <bits/stdc++.h>
using namespace std;
 
#define fastio ios_base::sync_with_stdio(false);cin.tie(NULL);
#define fr(i,a,b) for (int i = (a), _b = (b); i <= _b; i++)
#define frr(i,a,b) for (int i = (a), _b = (b); i >= _b; i--)
#define rep(i,n) for (int i = 0, _n = (n); i < _n; i++)
#define repr(i,n) for (long long i = (n) - 1; i >= 0; i--)
#define foreach(it,ar) for ( typeof(ar.begin()) it = ar.begin(); it != ar.end(); it++ )
#define ull unsigned long long int
#define ll long long int
#define ui unsigned int
#define pb push_back
 
#define PI 3.1415926535897932385
#define INF 1e9
#define EPS 1e-7
#define MAXN 1000000005
#define MOD 1000000007 
                              //          ★★ ASHWINI SHARMA ★★      
ll gcd(ll a, ll b) 
{ 
    if (a == 0) 
        return b; 
    return gcd(b % a, a); 
} 
ll exp(ll x, ll y, ll p)
{
    ll res = 1;   
    x = x % p;  
    while (y > 0)
    {
        if (y & 1)    
            res = (res*x) % p;
        y = y>>1;     
        x = (x*x) % p; 
    }
    return res;
}

vector<int> parent(200005);
vector<int> size(200005);

int find_set(int v) {
    if (v == parent[v])
        return v;
    return parent[v] = find_set(parent[v]);
}
void union_sets(int a, int b) {
    a = find_set(a);
    b = find_set(b);
    if (a != b) {
        if (size[a] < size[b])
            swap(a, b);
        parent[b] = a;
        size[a] += size[b];
    }
}

int main() {
    
    fastio;
    int n, m;
    cin >> n >> m;
    int grps = 1;
    for(int i=1;i<=n;i++)
    {
        parent[i] = i;
        size[i] = 1;
    }
    while(m--)
    {
        int x, y;
        cin >> x >> y;
        union_sets(x, y);
    }
    fr(i, 1, n)
    {
        int y = find_set(i);
        grps = max(grps, size[y]);
    }
    cout << grps;




    return 0; 
}

Compiler output:
a.cc: In function 'void union_sets(int, int)':
a.cc:54:13: error: reference to 'size' is ambiguous
   54 |         if (size[a] < size[b])
      |             ^~~~
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:2:
/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:43:13: note:                 'std::vector<int> size'
   43 | vector<int> size(200005);
      |             ^~~~
a.cc:54:23: error: reference to 'size' is ambiguous
   54 |         if (size[a] < size[b])
      |                       ^~~~
/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:43:13: note:                 'std::vector<int> size'
   43 | vector<int> size(200005);
      |             ^~~~
a.cc:57:9: error: reference to 'size' is ambiguous
   57 |         size[a] += size[b];
      |         ^~~~
/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:43:13: note:                 'std::vector<int> size'
   43 | vector<int> size(200005);
      |             ^~~~
a.cc:57:20: error: reference to 'size' is ambiguous
   57 |         size[a] += size[b];
      |                    ^~~~
/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:43:13: note:                 'std::vector<int> size'
   43 | vector<int> size(200005);
      |             ^~~~
a.cc: In function 'int main()':
a.cc:70:9: error: reference to 'size' is ambiguous
   70 |         size[i] = 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:43:13: note:                 'std::vector<int> size'
   43 | vector<int> size(200005);
      |             ^~~~
a.cc:81:26: error: reference to 'size' is ambiguous
   81 |         grps = max(grps, size[y]);
      |                          ^~~~
/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:43:13: note:                 'std::vector<int> size'
   43 | vector<int> size(200005);
      |             ^~~~