Language: C++

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; i++)
using namespace std;
typedef long long ll;

int main() {
    int n;
    cin >> n;
    vector<string> ss(n);
    rep(i, n) {
        cin >> ss[i];
    }
    map<string, int> anagrams;
    rep(i, n) {
        string s = ss[i];
        sort(s.begin(), s.end());
        if (anagrams[s]) {
            anagrams[s]++;
        } else {
            anagrams[s] = 1;
        }
    }
    ll result = 0;
    for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
        if (i->second > 1) {
            result += i->second * (i->second - 1) / 2;
        }
    }
    cout << result << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:24:39: error: no match for 'operator<' (operand types are 'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' and 'std::map<std::__cxx11::basic_string<char>, int>::iterator' {aka 'std::_Rb_tree<std::__cxx11::basic_string<char>, std::pair<const std::__cxx11::basic_string<char>, int>, std::_Select1st<std::pair<const std::__cxx11::basic_string<char>, int> >, std::less<std::__cxx11::basic_string<char> >, std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> > >::iterator'})
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                     ~ ^ ~~~~~~~~~~~~~~
      |                                     |               |
      |                                     |               _Rb_tree_iterator<[...]>
      |                                     _Rb_tree_iterator<[...]>
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1143:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1143 |     operator<(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1143:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
/usr/include/c++/14/bits/regex.h:1224:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1224 |     operator<(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1224:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
/usr/include/c++/14/bits/regex.h:1317:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1317 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1317:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
/usr/include/c++/14/bits/regex.h:1391:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1391 |     operator<(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1391:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::map<std::__cxx11::basic_string<char>, int>::iterator' {aka 'std::_Rb_tree<std::__cxx11::basic_string<char>, std::pair<const std::__cxx11::basic_string<char>, int>, std::_Select1st<std::pair<const std::__cxx11::basic_string<char>, int> >, std::less<std::__cxx11::basic_string<char> >, std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> > >::iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
/usr/include/c++/14/bits/regex.h:1485:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1485 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1485:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
/usr/include/c++/14/bits/regex.h:1560:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1560 |     operator<(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1560:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::map<std::__cxx11::basic_string<char>, int>::iterator' {aka 'std::_Rb_tree<std::__cxx11::basic_string<char>, std::pair<const std::__cxx11::basic_string<char>, int>, std::_Select1st<std::pair<const std::__cxx11::basic_string<char>, int> >, std::less<std::__cxx11::basic_string<char> >, std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> > >::iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
/usr/include/c++/14/bits/regex.h:1660:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1660 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1660:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 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_pair.h:1045:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1045 |     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1045:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::pair<_T1, _T2>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:448:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  448 |     operator<(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::reverse_iterator<_Iterator>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
/usr/include/c++/14/bits/stl_iterator.h:493:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  493 |     operator<(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::reverse_iterator<_Iterator>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1694 |     operator<(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::move_iterator<_IteratorL>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1760 |     operator<(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note:   template argument deduction/substitution failed:
a.cc:24:54: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::move_iterator<_IteratorL>'
   24 |     for (auto i = anagrams.begin(); i < anagrams.end(); i++) {
      |                                                      ^
In file included from /usr/include/c++/14/bits/basic_string.h