Language: C++

#include <bits/stdc++.h>

using namespace std;

/*******  All Required define Pre-Processors and typedef Constants *******/
#define in1(n) cin>>n;
#define in2(n, k) cin>>n>>k;
#define in3(n, k, s) cin>>n>>k>>s;
#define scn(t) scanf("%d", &t)
#define scnld(t) scanf("%ld", &t)
#define scnlld(t) scanf("%lld", &t)
#define scnc(t) scanf("%c", &t)
#define scns(t) scanf("%s", t)
#define scnf(t) scanf("%f", &t)
#define scnlf(t) scanf("%lf", &t)
#define mem(a, b) memset(a, (b), sizeof(a))
#define nloop(i, j, k, in) for (int i = j; i < k; i += in)
#define rloop(i, j, k, in) for (int i = j; i >= k; i -= in)
#define rep(i, j) nloop(i, 0, j, 1)
#define rrep(i, j) rloop(i, j, 0, 1)
#define inar(n, a) \
    rep(i, n)\
        cin>>a[i];
#define all(cont) cont.begin(), cont.end()
#define rall(cont) cont.end(), cont.begin()
#define foreach(it, l) for (auto it = l.begin(); it != l.end(); it++)
#define IN(A, B, C) assert(B <= A && A <= C)
#define MP make_pair
#define PB push_back
bool sortbysec(const pair<int, int> &a, const pair<int, int> &b)\
{\
return (a.second < b.second);\
}
#define max3(a,b,c) max(a,max(b,c))
#define min3(a,b,c) min(a,min(b,c))
#define fast  \
    ios_base::sync_with_stdio(false);\
    cin.tie(NULL);
#define INF (int)1e9
#define EPS 1e-9
#define PI 3.1415926535897932384626433832795
#define MOD 1000000007
#define read(type) readInt<type>()
#define test  \
    int t;    \
    cin >> t; \
    while (t--)
const double pi = acos(-1.0);
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<string> VS;
typedef vector<PII> VII;
typedef vector<VI> VVI;
typedef map<int, int> MPII;
typedef set<int> SETI;
typedef multiset<int> MSETI;
typedef long int int32;
typedef unsigned long int uint32;
typedef long long int int64;
typedef unsigned long long int uint64;

vector<int> size(200002);
vector<int> parent(200002);

void make_set(int v)
{
    parent[v] = v;
    size[v] = 1;
}

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()
{
    fast
    int n, m;
    in2(n, m)
    rep(i, n) make_set(i+1);
    while(m--)
    {
        int x, y;
        in2(x, y)
        union_sets(x, y);
    }
    // rep(i, n) cout<<parent[i+1]<<" ";
    // cout<<"\n";
    cout<<*max_element(all(size));
    return 0;
}

Compiler output:
a.cc: In function 'void make_set(int)':
a.cc:68:5: error: reference to 'size' is ambiguous
   68 |     size[v] = 1;
      |     ^~~~
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:62:13: note:                 'std::vector<int> size'
   62 | vector<int> size(200002);
      |             ^~~~
a.cc: In function 'void union_sets(int, int)':
a.cc:84:13: error: reference to 'size' is ambiguous
   84 |         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:62:13: note:                 'std::vector<int> size'
   62 | vector<int> size(200002);
      |             ^~~~
a.cc:84:23: error: reference to 'size' is ambiguous
   84 |         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:62:13: note:                 'std::vector<int> size'
   62 | vector<int> size(200002);
      |             ^~~~
a.cc:87:9: error: reference to 'size' is ambiguous
   87 |         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:62:13: note:                 'std::vector<int> size'
   62 | vector<int> size(200002);
      |             ^~~~
a.cc:87:20: error: reference to 'size' is ambiguous
   87 |         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:62:13: note:                 'std::vector<int> size'
   62 | vector<int> size(200002);
      |             ^~~~
a.cc: In function 'int main()':
a.cc:105:28: error: reference to 'size' is ambiguous
  105 |     cout<<*max_element(all(size));
      |                            ^~~~
a.cc:24:19: note: in definition of macro 'all'
   24 | #define all(cont) cont.begin(), cont.end()
      |                   ^~~~
/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:62:13: note:                 'std::vector<int> size'
   62 | vector<int> size(200002);
      |             ^~~~
a.cc:105:28: error: reference to 'size' is ambiguous
  105 |     cout<<*max_element(all(size));
      |                            ^~~~
a.cc:24:33: note: in definition of macro 'all'
   24 | #define all(cont) cont.begin(), cont.end()
      |                                 ^~~~
/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:62:13: note:                 'std::vector<int> size'
   62 | vector<int> size(200002);
      |             ^~~~