Language: C++

#include<bits/stdc++.h>
//#include<ext/pb_ds/assoc_container.hpp>
using namespace std;
//using namespace __gnu_pbds;
const int inf=0x3f3f3f3f;
const double eps=1e-6;
const int mod=1000000007;
typedef long long ll;
int modpow(int x,int y,int md){if(y==0)return 1;int ret=modpow(x,y>>1,md);ret=(ll)ret*ret%md;if(y&1)ret=(ll)ret*x%md;return ret;}
struct Num{
	string s="";
	bool operator<(Num b){
		return s.size()<b.s.size()||(s.size()==b.s.size()&&s<b.s);
	}
	bool operator>(Num b){
		return s.size()>b.s.size()||(s.size()==b.s.size()&&s>b.s);
	}
	Num add(int x){
		Num ret=*this;
		ret.s.push_back('0'+x);
		return ret;
	}
	Num operator=(int x){
		s=to_string(x);
		return *this;
	}
	Num operator=(Num b){
		s=b.s;
		return *this; 
	}
}dp[10010];
const int cost[]={100000,2,5,5,4,5,6,3,7,6};
int main(){
	int n,m;
	cin>>n>>m;
	vector<int>a(m);
	for(int i=0;i<m;i++)cin>>a[i];
	for(int i=0;i<=n;i++){
		if(i&&dp[i]=="")continue;
		for(auto x:a){
			if(dp[i].add(x)>dp[i+cost[x]]){
				dp[i+cost[x]]=dp[i].add(x);
			}
		}
	}
	cout<<dp[n].s<<endl;
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:39:28: error: no match for 'operator==' (operand types are 'Num' and 'const char [1]')
   39 |                 if(i&&dp[i]=="")continue;
      |                       ~~~~~^~~~
      |                           |  |
      |                           |  const char [1]
      |                           Num
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:1103:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1103 |     operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1103:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'Num' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
/usr/include/c++/14/bits/regex.h:1199:5: 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>&)'
 1199 |     operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1199:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'Num' is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
/usr/include/c++/14/bits/regex.h:1274:5: 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>&)'
 1274 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1274:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'Num' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
/usr/include/c++/14/bits/regex.h:1366:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1366 |     operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1366:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'const char [1]'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
/usr/include/c++/14/bits/regex.h:1441:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1441 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1441:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'Num' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
/usr/include/c++/14/bits/regex.h:1534:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1534 |     operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1534:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'const char [1]'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
/usr/include/c++/14/bits/regex.h:1613:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1613 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1613:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'Num' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
/usr/include/c++/14/bits/regex.h:2186:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator==(const match_results<_BiIter, _Alloc>&, const match_results<_BiIter, _Alloc>&)'
 2186 |     operator==(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:2186:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'Num' is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
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: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:39:30: note:   'Num' is not derived from 'const std::pair<_T1, _T2>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
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:39:30: note:   'Num' is not derived from 'const std::reverse_iterator<_Iterator>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
/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:39:30: note:   'Num' is not derived from 'const std::reverse_iterator<_Iterator>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
/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:39:30: note:   'Num' is not derived from 'const std::move_iterator<_IteratorL>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
/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:39:30: note:   'Num' is not derived from 'const std::move_iterator<_IteratorL>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
In file included from /usr/include/c++/14/bits/char_traits.h:42,
                 from /usr/include/c++/14/string:42,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/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:39:30: note:   'Num' is not derived from 'const std::fpos<_StateT>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
In file included from /usr/include/c++/14/string:43:
/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:39:30: note:   'Num' is not derived from 'const std::allocator<_CharT>'
   39 |                 if(i&&dp[i]=="")continue;
      |                              ^~
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:39:30: note:   'Num' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   39 |                 if(i&&dp[i]=="")continue;
      |