Language: C++

#include <iostream>
#include <algorithm>
#include <vector>
#include <stdio.h>
#define ll long long
using namespace std;

class UnionFindForests{
    public:
        vector<ll> parents, ranks;
        UnionFindForests(ll size){
            for (ll i = 0; i < size; ++i)
            {
                parents.push_back(i);
                ranks.push_back(0);
            }
        }

        ll find(ll x){
            if(parents[x] == x){
                return x;
            }else{
                //???????????????????????£?????´???????????´??\??????????????´????????????
                //pass compression(????????§???)
                return parents[x] = find(parents[x]);
            }
        }

        bool same(ll x, ll y){
            if(parents[x] == parents[y]){
                return true;
            }else{
                return false;
            }
        }

        void unite(ll x, ll y){
            ll root_x = find(x);
            ll root_y = find(y);
            if (ranks[root_x] > ranks[root_y])
            {
                parents[root_y] = root_x;
            }else if(ranks[root_x] < ranks[root_y]){
                parents[root_x] = root_y;
            }else if(ranks[root_x] == ranks[root_y]){
                parents[root_x] = root_y;
                ranks[root_y]++;
            }
        }
};

class Edge{ 
public:
	ll source, target, cost;
	
	Edge(ll source = 0, ll target = 0, ll cost = 0)
	:source(source)
	,target(target)
	,cost(cost){}

	static bool compare(const Edge& e1, const Edge& e2){
		return e1.cost < e2.cost;
	}
};

ll V, E;
vector<Edge> edges;

ll kluskal(){
	ll min_cost = 0;
	sort(edges, edges + E, Edge::compare);
	UnionFindForests uf = UnionFindForests(V);
	for (int i = 0; i < E; ++i)
	{
		if(uf.same(edges[i].source, edges[i].target) == false){
			uf.unite(edges[i].source, edges[i].target);
			min_cost+= edges[i].cost;
		}
	}
	return min_cost;
}


int main(){
	cin >> V >> E;
	for (int i = 0; i < E; ++i)
	{
		ll source, target, cost;
		scanf("%lld %lld %lld", &source, &target, &cost);
		// cin >> source >> target >> cost;
		edges.push_back(Edge(source, target, cost)); 
	}

	ll ans = kluskal();
	cout << ans << endl;
    return 0;
}

Compiler output:
a.cc: In function 'long long int kluskal()':
a.cc:71:27: error: no match for 'operator+' (operand types are 'std::vector<Edge>' and 'long long int')
   71 |         sort(edges, edges + E, Edge::compare);
      |                     ~~~~~ ^ ~
      |                     |       |
      |                     |       long long int
      |                     std::vector<Edge>
In file included from /usr/include/c++/14/string:48,
                 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.h:627:5: note: candidate: 'template<class _Iterator> constexpr std::reverse_iterator<_Iterator> std::operator+(typename reverse_iterator<_Iterator>::difference_type, const reverse_iterator<_Iterator>&)'
  627 |     operator+(typename reverse_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:627:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'long long int'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note: candidate: 'template<class _Iterator> constexpr std::move_iterator<_IteratorL> std::operator+(typename move_iterator<_IteratorL>::difference_type, const move_iterator<_IteratorL>&)'
 1798 |     operator+(typename move_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'long long int'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
In file included from /usr/include/c++/14/string:54:
/usr/include/c++/14/bits/basic_string.h:3598:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3598 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3598:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   'std::vector<Edge>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3616:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3616 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3616:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   mismatched types 'const _CharT*' and 'std::vector<Edge>'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3635:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3635 |     operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Alloc>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3635:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'long long int'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3652:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3652 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3652:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   'std::vector<Edge>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3670:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, _CharT)'
 3670 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, _CharT __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3670:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   'std::vector<Edge>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3682:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3682 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3682:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   'std::vector<Edge>' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3689:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3689 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3689:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   'std::vector<Edge>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3696:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3696 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3696:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   'std::vector<Edge>' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3719:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3719 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3719:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   mismatched types 'const _CharT*' and 'std::vector<Edge>'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3726:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3726 |     operator+(_CharT __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3726:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'long long int'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3733:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const _CharT*)'
 3733 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3733:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   'std::vector<Edge>' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3740:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, _CharT)'
 3740 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3740:5: note:   template argument deduction/substitution failed:
a.cc:71:29: note:   'std::vector<Edge>' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   71 |         sort(edges, edges + E, Edge::compare);
      |                             ^