Language: C++

#include <algorithm>
#include <iostream>
#include <vector>
#include <map>
using namespace std;
typedef long long ll;

const int MAXN = 1e5 + 10;
vector<pair<int, int> > edg;
pair<ll, int> d[MAXN];
vector<int> Mat[MAXN];
int n, cnt[MAXN];
map<ll, int> mp;
bool se[MAXN];
ll dist;
int num;

void dfs(int v, int di) {
	se[v] = 1, num++;
	dist += di;
	for (int i = 0; i < Mat[v].size(); i++)
		if (!se[Mat[v][i]])
			dfs(Mat[v][i], di + 1);
}

int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> d[i - 1].first;
		mp[d[i - 1].first] = i;
		d[i - 1].second = i;
		cnt[i] = 1;
	}
	sort(d, d + n);
	reverse(d, d + n);
	for (int i = 0; i < n - 1; i++) {
		int k = cnt[d[i].second];
		if (2 * k > n || mp.find(d[i].first + k - (n - k)) == mp.end())
			return cout << -1, 0;
		cnt[mp[d[i].first + k - (n - k)]] += k;
		edg.push_back({d[i].second, mp[d[i].first + k - (n - k)]});
		Mat[mp[d[i].first + k - (n - k)]].push_back(d[i].second);
		Mat[d[i].second].push_back(mp[d[i].first + k - (n - k)]);
	}
	dfs(1);
	if (dist == d[1] && num == n && edg.size() == n - 1) {
		for (int i = 0; i < edg.size(); i++)
			cout << edg[i].first << ' ' << edg[i].second << endl;
		return 0;
	}
	cout << -1;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:45:12: error: too few arguments to function 'void dfs(int, int)'
   45 |         dfs(1);
      |         ~~~^~~
a.cc:18:6: note: declared here
   18 | void dfs(int v, int di) {
      |      ^~~
a.cc:46:18: error: no match for 'operator==' (operand types are 'll' {aka 'long long int'} and 'std::pair<long long int, int>')
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |             ~~~~ ^~ ~~~~
      |             |          |
      |             |          std::pair<long long int, int>
      |             ll {aka long long int}
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_pair.h:1033:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator==(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1033 |     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1033:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'const std::pair<_T1, _T2>' and 'll' {aka 'long long int'}
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:441:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  441 |     operator==(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:441:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'll' {aka 'long long int'}
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
/usr/include/c++/14/bits/stl_iterator.h:486:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  486 |     operator==(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:486:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'll' {aka 'long long int'}
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1667 |     operator==(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'll' {aka 'long long int'}
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1737 |     operator==(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'll' {aka 'long long int'}
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
In file included from /usr/include/c++/14/iosfwd:42,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:2:
/usr/include/c++/14/bits/postypes.h:192:5: note: candidate: 'template<class _StateT> bool std::operator==(const fpos<_StateT>&, const fpos<_StateT>&)'
  192 |     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:192:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'const std::fpos<_StateT>' and 'll' {aka 'long long int'}
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
In file included from /usr/include/c++/14/string:43,
                 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:
/usr/include/c++/14/bits/allocator.h:235:5: note: candidate: 'template<class _T1, class _T2> bool std::operator==(const allocator<_CharT>&, const allocator<_T2>&)'
  235 |     operator==(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:235:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'const std::allocator<_CharT>' and 'll' {aka 'long long int'}
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:629:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  629 |     operator==(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:629:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'long long int'
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
/usr/include/c++/14/string_view:637:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  637 |     operator==(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:637:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'long long int'
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
/usr/include/c++/14/string_view:644:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  644 |     operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:644:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   'std::pair<long long int, int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
/usr/include/c++/14/bits/basic_string.h:3755:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3755 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3755:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'll' {aka 'long long int'}
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
/usr/include/c++/14/bits/basic_string.h:3772:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3772 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3772:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'll' {aka 'long long int'}
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
/usr/include/c++/14/bits/basic_string.h:3819:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3819 |     operator==(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3819:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'const _CharT*' and 'long long int'
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/tuple:2558:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator==(const tuple<_UTypes ...>&, const tuple<_Elements ...>&)'
 2558 |     operator==(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/14/tuple:2558:5: note:   template argument deduction/substitution failed:
a.cc:46:24: note:   mismatched types 'const std::tuple<_UTypes ...>' and 'll' {aka 'long long int'}
   46 |         if (dist == d[1] && num == n && edg.size() == n - 1) {
      |                        ^
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:234:5: note: candidate: 'template<class _CharT, class _Traits> bool std::operator==(const istreambuf