Language: C++

#include <iostream>
#include <cstdio>
#define N 2
using namespace std;

class Calc{
    public:
    double A[N][N+1];
    int i, j, k;

    void calcSi();
    void printSi();
}

void Calc::calcSi(){
    for(i=0;i<N-1;i++){
        for(j=i+1;j<N;j++){
            int tmp = A[j][i] / A[i][i];
            for(k=i+1; k<=N; k++)
                A[j][k] -= A[i][k] * tmp;
        }
    }

    for(i=N-1; i>=0; i--){
        tmp = A[i][N];
        for(j=i+1;j<N;j++)
            tmp -= A[i][j] * A[j][N];
        A[i][N] = tmp / A[i][i];
    }
}

void Calc::printSi(){
    for(i=0;i<N;i++){
        printf("%.3f",A[i][N]);
        if(i != N) {
            cout << " ";
        }
    }
    cout << endl;
}

int main(void){
    Calc c;
    int i;
    while(cout >> c.A[0][0] >> c.A[0][1] >> c.A[0][2] >> c.A[1][0] >> c.A[1][1] >> c.A[1][2])
    {
        c.calcSi();
        c.printSi();
    }
    return 0;
}

Compiler output:
a.cc:13:2: error: expected ';' after class definition
   13 | }
      |  ^
      |  ;
a.cc: In member function 'void Calc::calcSi()':
a.cc:25:9: error: 'tmp' was not declared in this scope; did you mean 'tm'?
   25 |         tmp = A[i][N];
      |         ^~~
      |         tm
a.cc: In function 'int main()':
a.cc:45:16: error: no match for 'operator>>' (operand types are 'std::ostream' {aka 'std::basic_ostream<char>'} and 'double')
   45 |     while(cout >> c.A[0][0] >> c.A[0][1] >> c.A[0][2] >> c.A[1][0] >> c.A[1][1] >> c.A[1][2])
      |           ~~~~ ^~ ~~~~~~~~~
      |           |               |
      |           |               double
      |           std::ostream {aka std::basic_ostream<char>}
In file included from /usr/include/c++/14/string:55,
                 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,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/basic_string.tcc:835:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
  835 |     operator>>(basic_istream<_CharT, _Traits>& __in,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.tcc:835:5: note:   template argument deduction/substitution failed:
a.cc:45:27: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'std::basic_istream<_CharT, _Traits>'
   45 |     while(cout >> c.A[0][0] >> c.A[0][1] >> c.A[0][2] >> c.A[1][0] >> c.A[1][1] >> c.A[1][2])
      |                           ^
In file included from /usr/include/c++/14/bits/memory_resource.h:38,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/cstddef:131:5: note: candidate: 'template<class _IntegerType> constexpr std::__byte_op_t<_IntegerType> std::operator>>(byte, _IntegerType)'
  131 |     operator>>(byte __b, _IntegerType __shift) noexcept
      |     ^~~~~~~~
/usr/include/c++/14/cstddef:131:5: note:   template argument deduction/substitution failed:
a.cc:45:11: note:   cannot convert 'std::cout' (type 'std::ostream' {aka 'std::basic_ostream<char>'}) to type 'std::byte'
   45 |     while(cout >> c.A[0][0] >> c.A[0][1] >> c.A[0][2] >> c.A[1][0] >> c.A[1][1] >> c.A[1][2])
      |           ^~~~
In file included from /usr/include/c++/14/istream:1109,
                 from /usr/include/c++/14/iostream:42:
/usr/include/c++/14/bits/istream.tcc:978:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT&)'
  978 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
      |     ^~~~~~~~
/usr/include/c++/14/bits/istream.tcc:978:5: note:   template argument deduction/substitution failed:
a.cc:45:27: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'std::basic_istream<_CharT, _Traits>'
   45 |     while(cout >> c.A[0][0] >> c.A[0][1] >> c.A[0][2] >> c.A[1][0] >> c.A[1][1] >> c.A[1][2])
      |                           ^
/usr/include/c++/14/istream:849:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, unsigned char&)'
  849 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
      |     ^~~~~~~~
/usr/include/c++/14/istream:849:5: note:   template argument deduction/substitution failed:
a.cc:45:27: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'std::basic_istream<char, _Traits>'
   45 |     while(cout >> c.A[0][0] >> c.A[0][1] >> c.A[0][2] >> c.A[1][0] >> c.A[1][1] >> c.A[1][2])
      |                           ^
/usr/include/c++/14/istream:854:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, signed char&)'
  854 |     operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
      |     ^~~~~~~~
/usr/include/c++/14/istream:854:5: note:   template argument deduction/substitution failed:
a.cc:45:27: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'std::basic_istream<char, _Traits>'
   45 |     while(cout >> c.A[0][0] >> c.A[0][1] >> c.A[0][2] >> c.A[1][0] >> c.A[1][1] >> c.A[1][2])
      |                           ^
/usr/include/c++/14/istream:896:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT*)'
  896 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:896:5: note:   template argument deduction/substitution failed:
a.cc:45:27: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'std::basic_istream<_CharT, _Traits>'
   45 |     while(cout >> c.A[0][0] >> c.A[0][1] >> c.A[0][2] >> c.A[1][0] >> c.A[1][1] >> c.A[1][2])
      |                           ^
/usr/include/c++/14/istream:939:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, unsigned char*)'
  939 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:939:5: note:   template argument deduction/substitution failed:
a.cc:45:27: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'std::basic_istream<char, _Traits>'
   45 |     while(cout >> c.A[0][0] >> c.A[0][1] >> c.A[0][2] >> c.A[1][0] >> c.A[1][1] >> c.A[1][2])
      |                           ^
/usr/include/c++/14/istream:945:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, signed char*)'
  945 |     operator>>(basic_istream<char, _Traits>& __in, signed char* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:945:5: note:   template argument deduction/substitution failed:
a.cc:45:27: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'std::basic_istream<char, _Traits>'
   45 |     while(cout >> c.A[0][0] >> c.A[0][1] >> c.A[0][2] >> c.A[1][0] >> c.A[1][1] >> c.A[1][2])
      |                           ^
/usr/include/c++/14/istream:1099:5: note: candidate: 'template<class _Istream, class _Tp> _Istream&& std::operator>>(_Istream&&, _Tp&&)'
 1099 |     operator>>(_Istream&& __is, _Tp&& __x)
      |     ^~~~~~~~
/usr/include/c++/14/istream:1099:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/istream: In substitution of 'template<class _Istream, class _Tp> _Istream&& std::operator>>(_Istream&&, _Tp&&) [with _Istream = std::basic_ostream<char>&; _Tp = double&]':
a.cc:45:27:   required from here
   45 |     while(cout >> c.A[0][0] >> c.A[0][1] >> c.A[0][2] >> c.A[1][0] >> c.A[1][1] >> c.A[1][2])
      |                           ^
/usr/include/c++/14/istream:1099:5: error: no type named 'type' in 'struct std::enable_if<false, void>'
 1099 |     operator>>(_Istream&& __is, _Tp&& __x)
      |     ^~~~~~~~