Language: C++

#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

struct edge{
	int u;	//?????????
	int v;	//??°??????
	int cost;	//??????
	//???????????????????????§?????§?°???¢????????????
	bool operator<(const edge& another) const {
			return cost < another.cost;
	}
};

const int MAX_N = 100;
const int MAX_M = 10000;

edge es[MAX_M];
int par[MAX_N];
int rank[MAX_N];

void initial(int n){		//?????????
	for(int i=0;i<n;i++){
		par[i] = i;
		rank[i] = 0;
	}
}

int find(int x){		//??¨??????????±???????
	if(par[x] == x){
		return x;
	}else{
		return par[x] = find(par[x],par);
	}
}

void unite(int x,int y){	//x???????????¨??¨y???????????¨?????????
	x = find(x,par);	//x???????????¨??????????????????x??¨??????
	y = find(y,par);	//y???????????¨??????????????????y??¨??????
	if(x == y) return;
	if(rank[x] < rank[y]){
		par[x] = y;
	}else{
		par[y] = x;
		if(rank[x] == rank[y])
			rank[x]++;
	}
}

bool same(int x,int y){	//x,y???????????¨???????????§?????????
	return find(x,par) == find(y,par);
}

bool comp(const edge& e1,const edge& e2){
	return e1.cost < e2.cost;
}

int kruskal(int n,int m){
	initial(n,par,rank);
	int res = 0;
	for(int i=0;i<m;i++){
		edge e = es[i];
		if(!same(e.u,e.v,par)){
			unite(e.u,e.v,par,rank);
			res += e.cost;
		}
	}
	return res;
}

int main(){
	int n,m=0,k,l,x;
	cin >> n;	//????????°?????\???
	int cnt=0;
	for(int i=0;i<n;i++){
		for(int j=0;j<n;j++){
			cin >> x;
			if(x != -1){
				edge e;
				e.from = i; e.to = j; e.cost = x;
				es[m] = e;
				m++;
			}
		}
	}
	sort(es,es+m);
	cout << kruskal(n,m) << "\n";
}

Compiler output:
a.cc: In function 'void initial(int)':
a.cc:27:17: error: reference to 'rank' is ambiguous
   27 |                 rank[i] = 0;
      |                 ^~~~
In file included from /usr/include/c++/14/bits/move.h:37,
                 from /usr/include/c++/14/bits/exception_ptr.h:41,
                 from /usr/include/c++/14/exception:166,
                 from /usr/include/c++/14/ios:41,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/type_traits:1437:12: note: candidates are: 'template<class> struct std::rank'
 1437 |     struct rank
      |            ^~~~
a.cc:22:5: note:                 'int rank [100]'
   22 | int rank[MAX_N];
      |     ^~~~
a.cc: In function 'int find(int)':
a.cc:35:37: error: no matching function for call to 'find(int&, int [100])'
   35 |                 return par[x] = find(par[x],par);
      |                                 ~~~~^~~~~~~~~~~~
In file included from /usr/include/c++/14/bits/locale_facets.h:48,
                 from /usr/include/c++/14/bits/basic_ios.h:37,
                 from /usr/include/c++/14/ios:46:
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note: candidate: 'template<class _CharT2> typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(istreambuf_iterator<_CharT>, istreambuf_iterator<_CharT>, const _CharT2&)'
  435 |     find(istreambuf_iterator<_CharT> __first,
      |     ^~~~
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:3:
/usr/include/c++/14/bits/stl_algo.h:3842:5: note: candidate: 'template<class _IIter, class _Tp> _IIter std::find(_IIter, _IIter, const _Tp&)'
 3842 |     find(_InputIterator __first, _InputIterator __last,
      |     ^~~~
/usr/include/c++/14/bits/stl_algo.h:3842:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:86:
/usr/include/c++/14/pstl/glue_algorithm_defs.h:60:1: note: candidate: 'template<class _ExecutionPolicy, class _ForwardIterator, class _Tp> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator> std::find(_ExecutionPolicy&&, _ForwardIterator, _ForwardIterator, const _Tp&)'
   60 | find(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value);
      | ^~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:60:1: note:   candidate expects 4 arguments, 2 provided
a.cc:31:5: note: candidate: 'int find(int)'
   31 | int find(int x){                //??¨??????????±???????
      |     ^~~~
a.cc:31:5: note:   candidate expects 1 argument, 2 provided
a.cc: In function 'void unite(int, int)':
a.cc:40:17: error: no matching function for call to 'find(int&, int [100])'
   40 |         x = find(x,par);        //x???????????¨??????????????????x??¨??????
      |             ~~~~^~~~~~~
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note: candidate: 'template<class _CharT2> typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(istreambuf_iterator<_CharT>, istreambuf_iterator<_CharT>, const _CharT2&)'
  435 |     find(istreambuf_iterator<_CharT> __first,
      |     ^~~~
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_algo.h:3842:5: note: candidate: 'template<class _IIter, class _Tp> _IIter std::find(_IIter, _IIter, const _Tp&)'
 3842 |     find(_InputIterator __first, _InputIterator __last,
      |     ^~~~
/usr/include/c++/14/bits/stl_algo.h:3842:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/pstl/glue_algorithm_defs.h:60:1: note: candidate: 'template<class _ExecutionPolicy, class _ForwardIterator, class _Tp> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator> std::find(_ExecutionPolicy&&, _ForwardIterator, _ForwardIterator, const _Tp&)'
   60 | find(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value);
      | ^~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:60:1: note:   candidate expects 4 arguments, 2 provided
a.cc:31:5: note: candidate: 'int find(int)'
   31 | int find(int x){                //??¨??????????±???????
      |     ^~~~
a.cc:31:5: note:   candidate expects 1 argument, 2 provided
a.cc:41:17: error: no matching function for call to 'find(int&, int [100])'
   41 |         y = find(y,par);        //y???????????¨??????????????????y??¨??????
      |             ~~~~^~~~~~~
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note: candidate: 'template<class _CharT2> typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(istreambuf_iterator<_CharT>, istreambuf_iterator<_CharT>, const _CharT2&)'
  435 |     find(istreambuf_iterator<_CharT> __first,
      |     ^~~~
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_algo.h:3842:5: note: candidate: 'template<class _IIter, class _Tp> _IIter std::find(_IIter, _IIter, const _Tp&)'
 3842 |     find(_InputIterator __first, _InputIterator __last,
      |     ^~~~
/usr/include/c++/14/bits/stl_algo.h:3842:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/pstl/glue_algorithm_defs.h:60:1: note: candidate: 'template<class _ExecutionPolicy, class _ForwardIterator, class _Tp> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator> std::find(_ExecutionPolicy&&, _ForwardIterator, _ForwardIterator, const _Tp&)'
   60 | find(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value);
      | ^~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:60:1: note:   candidate expects 4 arguments, 2 provided
a.cc:31:5: note: candidate: 'int find(int)'
   31 | int find(int x){                //??¨??????????±???????
      |     ^~~~
a.cc:31:5: note:   candidate expects 1 argument, 2 provided
a.cc:43:12: error: reference to 'rank' is ambiguous
   43 |         if(rank[x] < rank[y]){
      |            ^~~~
/usr/include/c++/14/type_traits:1437:12: note: candidates are: 'template<class> struct std::rank'
 1437 |     struct rank
      |            ^~~~
a.cc:22:5: note:                 'int rank [100]'
   22 | int rank[MAX_N];
      |     ^~~~
a.cc:43:22: error: reference to 'rank' is ambiguous
   43 |         if(rank[x] < rank[y]){
      |                      ^~~~
/usr/include/c++/14/type_traits:1437:12: note: candidates are: 'template<class> struct std::rank'
 1437 |     struct rank
      |            ^~~~
a.cc:22:5: note:                 'int rank [100]'
   22 | int rank[MAX_N];
      |     ^~~~
a.cc:47:20: error: reference to 'rank' is ambiguous
   47 |                 if(rank[x] == rank[y])
      |                    ^~~~
/usr/include/c++/14/type_traits:1437:12: note: candidates are: 'template<class> struct std::rank'
 1437 |     struct rank
      |            ^~~~
a.cc:22:5: note:                 'int rank [100]'
   22 | int rank[MAX_N];
      |     ^~~~
a.cc:47:31: error: reference to 'rank' is ambiguous
   47 |                 if(rank[x] == rank[y])
      |                               ^~~~
/usr/include/c++/14/type_traits:1437:12: note: candidates are: 'template<class> struct std::rank'
 1437 |     struct rank
      |            ^~~~
a.cc:22:5: note:                 'int rank [100]'
   22 | int rank[MAX_N];
      |     ^~~~
a.cc:48:25: error: reference to 'rank' is ambiguous
   48 |                         rank[x]++;
      |                         ^~~~
/usr/include/c++/14/type_traits:1437:12: note: candidates are: 'template<class> struct std::rank'
 1437 |     struct rank
      |            ^~~~
a.cc:22:5: note:                 'int rank [100]'
   22 | int rank[MAX_N];
      |     ^~~~
a.cc: In function 'bool same(int, int)':
a.cc:53:20: error: no matching function for call to 'find(int&, int [100])'
   53 |         return find(x,par) == find(y,par);
      |                ~~~~^~~~~~~
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note: candidate: 'template<class _CharT2> typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(istreambuf_iterator<_CharT>, istreambuf_iterator<_CharT>, const _CharT2&)'
  435 |     find(istreambuf_iterator<_CharT> __first,
      |     ^~~~
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_algo.h:3842:5: note: candidate: 'template<class _IIter, class _Tp> _IIter std::find(_IIter, _IIter, const _Tp&)'
 3842 |     find(_InputIterator __first, _InputIterator __last,
      |     ^~~~
/usr/include/c++/14/bits/stl_algo.h:3842:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/pstl/glue_algorithm_defs.h:60:1: note: candidate: 'template<class _ExecutionPolicy, class _ForwardIterator, class _Tp> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator> std::find(_ExecutionPolicy&&, _ForwardIterator, _ForwardIterator, const _Tp&)'
   60 | find(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value);
      | ^~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:60:1: note:   candidate expects 4 arguments, 2 provided
a.cc:31:5: note: candidate: 'int find(int)'
   31 | int find(int x){                //??¨??????????±???????
      |     ^~~~
a.cc:31:5: note:   candidate expects 1 argument, 2 provided
a.cc:53:35: error: no matching function for call to 'find(int&, int [100])'
   53 |         return find(x,par) == find(y,par);
      |                               ~~~~^~~~~~~
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note: candidate: 'template<class _CharT2> typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(istreambuf_iterator<_CharT>, istreambuf_iterator<_CharT>, const _CharT2&)'