Language: C++

#include <iostream>
#include <vector>
#include <queue>

using namespace std;
typedef pair<int, int> P;

void solve()
{
	int N;
	while(cin >> N, N)
	{
		vector<vector<P> > field(N, N);
		for(int i = 0; i < N; ++i)
		{
			for(int j = 0; j < N; ++j)
			{
				cin >> field[i][j].first >> field[i][j].second;
			}
		}
		bool isVisited[101][101];
		bool roopStart[101][101];
		for(int i = 0; i < N; ++i)
		{
			for(int j = 0; j < N; ++j)
			{
				isVisited[i][j] = false;
				roopStart[i][j] = false;
			}
		}
		for(int i = 0; i < N; ++i)
		{
			for(int j = 0; j < N; ++j)
			{
				int x = field[i][j].first;
				int y = field[i][j].second;
				bool roopFlag = false;
				while(isVisited[x][y] == false)
				{
					roopFlag = true;
					if(roopStart[x][y] == true)
					{
						break;
					}
					isVisited[x][y] = true;
					x = field[x][y].first;
					y = field[x][y].second;
				}
				if(roopFlag)
				{
					roopStart[x][y] = true;
				}
			}
		}
		int count = 0;
		for(int i = 0; i < N; ++i)
		{
			for(int j = 0; j < N; ++j)
			{
				if(roopStart[i][j] == true)
				{
					++count;
				}
			}
		}
		cout << count << endl;
	}
}

int main()
{
	solve();
	return(0);
}

Compiler output:
a.cc: In function 'void solve()':
a.cc:13:46: error: no matching function for call to 'std::vector<std::vector<std::pair<int, int> > >::vector(int&, int&)'
   13 |                 vector<vector<P> > field(N, N);
      |                                              ^
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:2:
/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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<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_iterator_base_funcs.h:66,
                 from /usr/include/c++/14/string:47,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<std::pair<int, int> > >; allocator_type = std::allocator<std::vector<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::vector<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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<std::pair<int, int> > >; std::__type_identity_t<_Alloc> = std::allocator<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:659:23: note:   no known conversion for argument 1 from 'int' to 'std::vector<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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<std::pair<int, int> > >; allocator_type = std::allocator<std::vector<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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<std::pair<int, int> > >; allocator_type = std::allocator<std::vector<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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<std::pair<int, int> > >; std::__type_identity_t<_Alloc> = std::allocator<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:624:28: note:   no known conversion for argument 1 from 'int' to 'const std::vector<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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<std::pair<int, int> > >; size_type = long unsigned int; value_type = std::vector<std::pair<int, int> >; allocator_type = std::allocator<std::vector<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::vector<std::pair<int, int> > >::value_type&' {aka 'const std::vector<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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<std::pair<int, int> > >; size_type = long unsigned int; allocator_type = std::allocator<std::vector<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::vector<std::pair<int, int> > >::allocator_type&' {aka 'const std::allocator<std::vector<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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<std::pair<int, int> > >; allocator_type = std::allocator<std::vector<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::vector<std::pair<int, int> >; _Alloc = std::allocator<std::vector<std::pair<int, int> > >]'
  531 |       vector() = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:531:7: note:   candidate expects 0 arguments, 2 provided