Language: C++

#include <bits/stdc++.h>
using namespace std;

int main() {
string s;
cin >> s;
int n=s.size();
string st[n][n][n];
for(int i=0;i<n;i++){
    for(int j=0;j<n;j++){
        st[i][j]=s.substr(i,j);
    }
}
int ans=0;
for(int i=0;i<n;i++){
    for(int j=0;j<n;j++){
        int length=st[i][j].size();
        for(int k=0;k<length;k++){
            if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
            ans=max(ans,length);
        }}
    }
}
cout << ans << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:11:17: error: incompatible types in assignment of 'std::__cxx11::basic_string<char>' to 'std::string [n]' {aka 'std::__cxx11::basic_string<char> [n]'}
   11 |         st[i][j]=s.substr(i,j);
      |         ~~~~~~~~^~~~~~~~~~~~~~
a.cc:17:29: error: request for member 'size' in 'st[i][j]', which is of non-class type 'std::string [n]' {aka 'std::__cxx11::basic_string<char> [n]'}
   17 |         int length=st[i][j].size();
      |                             ^~~~
a.cc:19:27: error: no match for 'operator==' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'char')
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                ~~~~~~~~~~~^~~~~
      |                          |  |
      |                          |  char
      |                          std::string {aka std::__cxx11::basic_string<char>}
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:19:29: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
/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:19:29: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
/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:19:29: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
/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:19:29: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
/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:19:29: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
/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:19:29: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
/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:19:29: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
/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:19:29: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
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:19:29: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::pair<_T1, _T2>'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
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:19:29: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
/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:19:29: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
/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:19:29: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
/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:19:29: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   19 |             if(st[i][j][k]=='A'||st[i][j][k]=='T'||st[i][j][k]=='G'||st[i][j][k]=='C'){
      |                             ^~~
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<_Sta