Language: C++

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

struct UnionFind {
    vector<int> par; // par[i]:iの親の番号　(例) par[3] = 2 : 3の親が2

    UnionFind(int N) : par(N) { //最初は全てが根であるとして初期化
        for(int i = 0; i < N; i++) par[i] = i;
    }

    int root(int x) { // データxが属する木の根を再帰で得る：root(x) = {xの木の根}
        if (par[x] == x) return x;
        return par[x] = root(par[x]);
    }

    void unite(int x, int y) { // xとyの木を併合
        int rx = root(x); //xの根をrx
        int ry = root(y); //yの根をry
        if (rx == ry) return; //xとyの根が同じ(=同じ木にある)時はそのまま
        par[rx] = ry; //xとyの根が同じでない(=同じ木にない)時：xの根rxをyの根ryにつける
    }

    bool same(int x, int y) { // 2つのデータx, yが属する木が同じならtrueを返す
        int rx = root(x);
        int ry = root(y);
        return rx == ry;
    }
};

int main() {
  int N;
  cin >> N;
  
  vector<tuple<int,int,int>> xy(N);
  UnionFind tree(N);
  
  long long ans = 0;
  
  for (int i=0; i<N; i++) {
    cin >> get<0>(xy[i]) >> get<1>(xy[i]);
    get<2>(xy[i]) = i;
  }
  
  sort(xy.begin(),xy.end());
  
  for (int i=0; i<N-1; i++) {
    if (get<0>(xy[i]) == get<0>(xy[i+1])) {
      tree.unite(get<2>(xy[i]),get<2>(xy[i+1]));
    }
  }
  for (int i=0; i<N; i++) {
    swap(get<0>(xy[i]),get<1>(xy[i]));
  }
  
  sort(xy.begin(),xy.end());

  for (int i=0; i<N-1; i++) {
    if (get<0>(xy[i]) == get<0>(xy[i+1])) {
      tree.unite(get<2>(xy[i]),get<2>(xy[i+1]));
    }
  }
  
  int p;
  for (int i=0; i<N; i++) {
    p = get<2>(xy[i]);
    get<2>(xy[i]) = tree.root(p);
    swap(get<0>(xy[i]),get<2>(xy[i]));
  }
  
  sort(xy.begin(),xy.end());
  
  long long num = 0;
  vector<pair<int,int>> can(N);
  vector<pair<int,int>> ansn(N,1);

  for (int i=0; i<N; i++) {
    if (i == N-1) {
      if (get<1>(xy[i]) != get<1>(xy[i]-1)) {
        ansn[get<0>(xy[i])].first++;
      }
    }
    if (get<0>(xy[i]) == get<0>(xy[i+1])) {
      if (get<1>(xy[i]) != get<1>(xy[i+1])) {
        ansn[get<0>(xy[i])].first++;
      }
    }
  }
      
  for (int i=0; i<N; i++) {
    swap(get<2>(xy[i]),get<1>(xy[i]));
  }
  
  for (int i=0; i<N; i++) {
    if (i == N-1) {
      if (get<1>(xy[i]) != get<1>(xy[i]-1)) {
        ansn[get<0>(xy[i])].second++;
      }
    }
    if (get<0>(xy[i]) == get<0>(xy[i+1])) {
      if (get<1>(xy[i]) != get<1>(xy[i+1])) {
        ansn[get<0>(xy[i])].second++;
      }
    }
  }
  
  for (int i=0; i<N; i++) {
    if (ansn[i].first != 1 && ansn[i].second != 1) {
      ans += ansn[i].first * ansn[i].second;
    }
  }
  
  cout << ans << endl;
  
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:74:33: error: no matching function for call to 'std::vector<std::pair<int, int> >::vector(int&, int)'
   74 |   vector<pair<int,int>> ansn(N,1);
      |                                 ^
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_vector.h:707:9: note: candidate: 'template<class _InputIterator, class> std::vector<_Tp, _Alloc>::vector(_InputIterator, _InputIterator, const allocator_type&) [with <template-parameter-2-2> = _InputIterator; _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >]'
  707 |         vector(_InputIterator __first, _InputIterator __last,
      |         ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:707:9: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/14/bits/stl_algobase.h:65,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_iterator_base_types.h: In substitution of 'template<class _InIter> using std::_RequireInputIter = std::__enable_if_t<((bool)std::is_convertible<typename std::iterator_traits< <template-parameter-1-1> >::iterator_category, std::input_iterator_tag>::value)> [with _InIter = int]':
/usr/include/c++/14/bits/stl_vector.h:705:9:   required from here
  705 |                typename = std::_RequireInputIter<_InputIterator>>
      |                ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator_base_types.h:252:57: error: no type named 'iterator_category' in 'struct std::iterator_traits<int>'
  252 |                                    input_iterator_tag>::value>;
      |                                                         ^~~~~
/usr/include/c++/14/bits/stl_vector.h:678:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::initializer_list<_Tp>, const allocator_type&) [with _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >; allocator_type = std::allocator<std::pair<int, int> >]'
  678 |       vector(initializer_list<value_type> __l,
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:678:43: note:   no known conversion for argument 1 from 'int' to 'std::initializer_list<std::pair<int, int> >'
  678 |       vector(initializer_list<value_type> __l,
      |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:659:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, std::__type_identity_t<_Alloc>&) [with _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >; std::__type_identity_t<_Alloc> = std::allocator<std::pair<int, int> >]'
  659 |       vector(vector&& __rv, const __type_identity_t<allocator_type>& __m)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:659:23: note:   no known conversion for argument 1 from 'int' to 'std::vector<std::pair<int, int> >&&'
  659 |       vector(vector&& __rv, const __type_identity_t<allocator_type>& __m)
      |              ~~~~~~~~~^~~~
/usr/include/c++/14/bits/stl_vector.h:640:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, const allocator_type&, std::false_type) [with _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >; allocator_type = std::allocator<std::pair<int, int> >; std::false_type = std::false_type]'
  640 |       vector(vector&& __rv, const allocator_type& __m, false_type)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:640:7: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_vector.h:635:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, const allocator_type&, std::true_type) [with _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >; allocator_type = std::allocator<std::pair<int, int> >; std::true_type = std::true_type]'
  635 |       vector(vector&& __rv, const allocator_type& __m, true_type) noexcept
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:635:7: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_vector.h:624:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&, std::__type_identity_t<_Alloc>&) [with _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >; std::__type_identity_t<_Alloc> = std::allocator<std::pair<int, int> >]'
  624 |       vector(const vector& __x, const __type_identity_t<allocator_type>& __a)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:624:28: note:   no known conversion for argument 1 from 'int' to 'const std::vector<std::pair<int, int> >&'
  624 |       vector(const vector& __x, const __type_identity_t<allocator_type>& __a)
      |              ~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:620:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&) [with _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >]'
  620 |       vector(vector&&) noexcept = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:620:7: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_vector.h:601:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&) [with _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >]'
  601 |       vector(const vector& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:601:7: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_vector.h:569:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(size_type, const value_type&, const allocator_type&) [with _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >; size_type = long unsigned int; value_type = std::pair<int, int>; allocator_type = std::allocator<std::pair<int, int> >]'
  569 |       vector(size_type __n, const value_type& __value,
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:569:47: note:   no known conversion for argument 2 from 'int' to 'const std::vector<std::pair<int, int> >::value_type&' {aka 'const std::pair<int, int>&'}
  569 |       vector(size_type __n, const value_type& __value,
      |                             ~~~~~~~~~~~~~~~~~~^~~~~~~
/usr/include/c++/14/bits/stl_vector.h:556:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(size_type, const allocator_type&) [with _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >; size_type = long unsigned int; allocator_type = std::allocator<std::pair<int, int> >]'
  556 |       vector(size_type __n, const allocator_type& __a = allocator_type())
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:556:51: note:   no known conversion for argument 2 from 'int' to 'const std::vector<std::pair<int, int> >::allocator_type&' {aka 'const std::allocator<std::pair<int, int> >&'}
  556 |       vector(size_type __n, const allocator_type& __a = allocator_type())
      |                             ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:542:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const allocator_type&) [with _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >; allocator_type = std::allocator<std::pair<int, int> >]'
  542 |       vector(const allocator_type& __a) _GLIBCXX_NOEXCEPT
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:542:7: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_vector.h:531:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector() [with _Tp = std::pair<int, int>; _Alloc = std::allocator<std::pair<int, int> >]'
  531 |       vector() = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:531:7: note:   candidate expects 0 arguments, 2 provided
a.cc:78:40: error: no match for 'operator-' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::tuple<int, int, int> >, std::tuple<int, int, int> >::value_type' {aka 'std::tuple<int, int, int>'} and 'int')
   78 |       if (get<1>(xy[i]) != get<1>(xy[i]-1)) {
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:618:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__y.base() - __x.base())) std::operator-(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  618 |     operator-(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:618:5: note:   template argument deduction/substitution failed:
a.cc:78:41: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::tuple<int, int, int> >, std::tuple<int, int, int> >::value_type' {aka 'std::tuple<int, int, int>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   78 |       if (get<1>(xy[i]) != get<1>(xy[i]-1)) {
      |                                         ^
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__x.base() - __y.base())) std::operator-(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1790 |     operator-(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note:   template argument deduction/substitution failed:
a.cc:78:41: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::tuple<int, int, int> >, std::tuple<int, int, int> >::value_type' {aka 'std::tuple<int, int, int>'} is not derived from 'const std::move_iterator<_IteratorL>'
   78 |       if (get<1>(xy[i]) != get<1>(xy[i]-1)) {
      |                                         ^
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/complex:370:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const complex<_Tp>&)'
  370 |     operator-(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:37