#include <iostream>

extern "C" void dgesv_(int *, int *, double *, int *, double *, double *, 
                       int *, int *);

// This function does nothing more than to set-up and execute a
// call to the DGESV routine from the LAPACK package.

int gaussian_elimination(double *A, double *b, int n)
{
   int c1 = n; // number of equations
   int c2 = 1; // number of right hand sides

   double *pivot = new double[n];
   int ok = 0; // output code

   dgesv_(&c1, &c2,(double *) A, &c1,(double *) pivot,(double *) b, &c1, &ok);

   delete pivot;
   return ok;
}

int main()
{
   int N;

   std::cout << "Enter the dimension of the problem: " << std::endl;
   std::cin >> N;
   std::cout << std::endl;
   
   double* A = new double[N*N];
   double* b = new double[N];

   for (int i=0; i<N; i++)
   {
      std::cout << "Enter row number "<< i <<": "<< std::endl;

      for (int k=0; k<N; k++)
      {
         std::cin >> A[i+k*N];
      }
   }

   std::cout << std::endl;
   std::cout << "Enter the right hand side: " << std::endl;
   for (int k=0; k<N; k++)
   {
      std::cin >>b[k];
   }

   gaussian_elimination(A, b, N);

   std::cout << std::endl;
   for (int i=0; i<N; i++)
      std::cout << "b[" << i << "]=" << b[i] << std::endl;

   delete A;
   delete b;
}

// g++ -c dgesv_example.cpp
// then
// f77 dgesv_example.o -L/usr/local/lib -llapack -lblas -lstdc++