Language: C++

/*
title:

url:

Kが５以下であることに注目
教訓
最初の方針よりも単純にかけた
まずは計算量を試算することが大事。あと、メモリ使用量
*/

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <functional>
#include <queue>
#include <limits>
#include <string>
#include <utility>
#include <cstring>
#include <map>
#include <cmath>

using namespace std;

#define REP(i, n) for (int i = 0; i < (n); i++)
#define INF 1000000007

typedef pair<int, int> pint;
typedef long long ll;

int main()
{
    string s;
    int k;
    cin >> s >> k;
    string ans[k];
    //find min alpahbet(a, b, c...)

    priority_queue<string, vector<string>, greater<string>> q;
    for (int i = 0; i < s.size(); i++)
    {
        string tmp = "";
        for (int j = 0; j + i < s.size(); j++)
        {
            tmp = tmp + s[i + j];
            q.push(tmp);
        }
    }
    string ans;
    for (int i = 0; i < n; i++)
    {
        ans = q.top();
        while (q.top() == ans)
        {
            q.pop();
        }
    }
    cout << ans << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:51:12: error: conflicting declaration 'std::string ans'
   51 |     string ans;
      |            ^~~
a.cc:38:12: note: previous declaration as 'std::string ans [k]'
   38 |     string ans[k];
      |            ^~~
a.cc:52:25: error: 'n' was not declared in this scope
   52 |     for (int i = 0; i < n; i++)
      |                         ^
a.cc:54:13: error: incompatible types in assignment of 'const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type' {aka 'const std::__cxx11::basic_string<char>'} to 'std::string [k]' {aka 'std::__cxx11::basic_string<char> [k]'}
   54 |         ans = q.top();
      |         ~~~~^~~~~~~~~
a.cc:55:24: error: no match for 'operator==' (operand types are 'const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type' {aka 'const std::__cxx11::basic_string<char>'} and 'std::string [k]' {aka 'std::__cxx11::basic_string<char> [k]'})
   55 |         while (q.top() == ans)
      |                ~~~~~~~ ^~ ~~~
      |                     |     |
      |                     |     std::string [k] {aka std::__cxx11::basic_string<char> [k]}
      |                     const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type {aka const std::__cxx11::basic_string<char>}
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:12:
/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:55:27: note:   'const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type' {aka 'const std::__cxx11::basic_string<char>'} is not derived from 'const std::fpos<_StateT>'
   55 |         while (q.top() == ans)
      |                           ^~~
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:55:27: note:   'const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type' {aka 'const std::__cxx11::basic_string<char>'} is not derived from 'const std::allocator<_CharT>'
   55 |         while (q.top() == ans)
      |                           ^~~
In file included from /usr/include/c++/14/string:48:
/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:55:27: note:   'const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type' {aka 'const std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   55 |         while (q.top() == ans)
      |                           ^~~
/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:55:27: note:   'const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type' {aka 'const std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   55 |         while (q.top() == ans)
      |                           ^~~
/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:55:27: note:   'const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type' {aka 'const std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   55 |         while (q.top() == ans)
      |                           ^~~
/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:55:27: note:   'const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type' {aka 'const std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   55 |         while (q.top() == ans)
      |                           ^~~
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: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:55:27: note:   'const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type' {aka 'const std::__cxx11::basic_string<char>'} is not derived from 'const std::pair<_T1, _T2>'
   55 |         while (q.top() == ans)
      |                           ^~~
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:55:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   55 |         while (q.top() == ans)
      |                           ^~~
/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:55:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   55 |         while (q.top() == ans)
      |                           ^~~
/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:55:27: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'std::string*' {aka 'std::__cxx11::basic_string<char>*'}
   55 |         while (q.top() == ans)
      |                           ^~~
/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:55:27: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'std::string [k]' {aka 'std::__cxx11::basic_string<char> [k]'}
   55 |         while (q.top() == ans)
      |                           ^~~
/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:55:27: note:   deduced conflicting types for parameter 'const _CharT' ('char' and 'std::string' {aka 'std::__cxx11::basic_string<