Language: C++

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

#define SWAP(A, B) {int tmp = (B); (B) = (A); (A) = (tmp);}

int main() {
	char word[100][31];
	int pagenum[100];
	int sortnum[100];
	int count;

	for (int i = 0; i < 100; i++)
		sortnum[i] = i;

	for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);

	for (int i = 0; i < count; i++) {
		for (int j = 0; j < count - i - 1; j++) {
			if (strcmp(word[sortnum[j]], word[sortnum[j+1]]) > 0)
				SWAP(sortnum[j], sortnum[j+1]);
		}
	}

	for (int i = 0; i < count; i++) {
		if (strcmp(word[sortnum[i]], word[sortnum[i+1]]) == 0) {
			int j, flag = 0;
			for (j = i
				; j < count - 1 && strcmp(word[sortnum[j]], word[sortnum[j+1]]) == 0
				; j++) 
			{
				if (pagenum[sortnum[j]] > pagenum[sortnum[j+1]]) {
					SWAP(sortnum[j], sortnum[j+1]);
					flag = 1;
				}
			}
			if (flag)
				i--;
			else
				i = j;
		}
	}

	for (int i = 0; i < count; i++) {
		cout << word[sortnum[i]] << endl;
		if (strcmp(word[sortnum[i]], word[sortnum[i+1]]) == 0) {
			for (; i < count && strcmp(word[sortnum[i]], word[sortnum[i+1]]) == 0; i++) {
				cout << pagenum[sortnum[i]] << ' ';
			}
		}
		cout << pagenum[sortnum[i]] << endl;
	}
			system("pause");
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:17:62: error: no match for 'operator!=' (operand types are 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} and 'long int')
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                              ^
a.cc:17:62: note: candidate: 'operator!=(int, long int)' (built-in)
a.cc:17:62: note:   no known conversion for argument 1 from 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} to 'int'
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:1:
/usr/include/c++/14/bits/postypes.h:197:5: note: candidate: 'template<class _StateT> bool std::operator!=(const fpos<_StateT>&, const fpos<_StateT>&)'
  197 |     operator!=(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:197:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/strings.h:23,
                 from /usr/include/string.h:462,
                 from /usr/include/c++/14/cstring:43,
                 from a.cc:3:
a.cc:17:65: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::fpos<_StateT>'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
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:243:5: note: candidate: 'template<class _T1, class _T2> bool std::operator!=(const allocator<_CharT>&, const allocator<_T2>&)'
  243 |     operator!=(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:243:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::allocator<_CharT>'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
In file included from /usr/include/c++/14/string:48:
/usr/include/c++/14/bits/stl_iterator.h:455:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  455 |     operator!=(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:455:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
/usr/include/c++/14/bits/stl_iterator.h:500:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  500 |     operator!=(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:500:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1686 |     operator!=(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1753 |     operator!=(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string:51:
/usr/include/c++/14/bits/stl_pair.h:1052:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator!=(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1052 |     operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1052:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::pair<_T1, _T2>'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
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:651:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  651 |     operator!=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:651:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   'std::basic_istream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
/usr/include/c++/14/string_view:658:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  658 |     operator!=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:658:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   'std::basic_istream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
/usr/include/c++/14/string_view:666:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  666 |     operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:666:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'long int'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
/usr/include/c++/14/bits/basic_string.h:3833:5: 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>&)'
 3833 |     operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3833:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
/usr/include/c++/14/bits/basic_string.h:3847:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3847 |     operator!=(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3847:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   mismatched types 'const _CharT*' and 'std::basic_istream<char>'
   17 |         for (count = 0; cin >> word[count] >> pagenum[count] != NULL; count++);
      |                                                                 ^~~~
/usr/include/c++/14/bits/basic_string.h:3860:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3860 |     operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3860:5: note:   template argument deduction/substitution failed:
a.cc:17:65: note:   'std::