Language: C++

#include<bits/stdc++.h>
using namespace std;
int main()
{
int n,k;
  cin >> n >> k;
vector<double> a[n];
  double max,sum;
  sum=0;
  for(int i=0;i<n;++i)
  {
  cin >> a.at(i);
  a[i]=(a[i]+1)/2;
    if(i<k) sum=sum+a.at(i);
  }
  max=sum;
  
  for(i=0;i<n-k-1;++i)
  {
  sum=sum-a.at(i)+a.at(i+k);
  if(sum > max) max=sum;
  }
  cout << max;
return 0;}

Compiler output:
a.cc: In function 'int main()':
a.cc:12:12: error: request for member 'at' in 'a', which is of non-class type 'std::vector<double> [n]'
   12 |   cin >> a.at(i);
      |            ^~
a.cc:13:13: error: no match for 'operator+' (operand types are 'std::vector<double>' and 'int')
   13 |   a[i]=(a[i]+1)/2;
      |         ~~~~^~
      |            | |
      |            | int
      |            std::vector<double>
In file included from /usr/include/c++/14/bits/stl_algobase.h:67,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:627:5: note: candidate: 'template<class _Iterator> constexpr std::reverse_iterator<_Iterator> std::operator+(typename reverse_iterator<_Iterator>::difference_type, const reverse_iterator<_Iterator>&)'
  627 |     operator+(typename reverse_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:627:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'int'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note: candidate: 'template<class _Iterator> constexpr std::move_iterator<_IteratorL> std::operator+(typename move_iterator<_IteratorL>::difference_type, const move_iterator<_IteratorL>&)'
 1798 |     operator+(typename move_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'int'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
In file included from /usr/include/c++/14/string:54,
                 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/basic_string.h:3598:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3598 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3598:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::vector<double>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/basic_string.h:3616:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3616 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3616:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   mismatched types 'const _CharT*' and 'std::vector<double>'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/basic_string.h:3635:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3635 |     operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Alloc>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3635:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/basic_string.h:3652:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3652 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3652:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::vector<double>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/basic_string.h:3670:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, _CharT)'
 3670 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, _CharT __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3670:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::vector<double>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/basic_string.h:3682:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3682 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3682:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::vector<double>' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/basic_string.h:3689:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3689 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3689:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::vector<double>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/basic_string.h:3696:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3696 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3696:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::vector<double>' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/basic_string.h:3719:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3719 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3719:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   mismatched types 'const _CharT*' and 'std::vector<double>'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/basic_string.h:3726:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3726 |     operator+(_CharT __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3726:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/basic_string.h:3733:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const _CharT*)'
 3733 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3733:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::vector<double>' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/bits/basic_string.h:3740:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, _CharT)'
 3740 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3740:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::vector<double>' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/complex:340:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator+(const complex<_Tp>&, const complex<_Tp>&)'
  340 |     operator+(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:340:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::vector<double>' is not derived from 'const std::complex<_Tp>'
   13 |   a[i]=(a[i]+1)/2;
      |              ^
/usr/include/c++/14/complex:349:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator+(