#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <conio.h>

#define DEGREE 9

double a[DEGREE][DEGREE], b[DEGREE];
char buffer[132];
int alpha, beta, gamma, size;
double store;

void main(void)
{
	printf("\n\nS U P E R    F A S T    M A T R I X     S O L V E R\n\n");
	do
	{
                printf("          ENTER THE DEGREE OF THE MATRIX\n\          THE DEGREE CAN ONLY BE [2<N<10]\n\          ZEROS ARE NOT ALLOWED ON THE PRINCIPLE DIAGONAL\n\n");
                size=atoi(gets(buffer));
	}
      while( ( size < 2 ) || ( size > DEGREE )  );

	printf("    ENTER THE COEFFICIENTS OF THE VARIABLES ROW BY ROW\n\n");

	for( alpha=0; alpha<size; alpha++)
	{
                for( beta=0; beta<size; beta++)
                {
                  printf("A(%d,%d)\n",alpha+1,beta+1);
			a[alpha][beta]=atof(gets(buffer));
                  if( (a[alpha][alpha] == 0.0) && (beta == alpha) )
                  {
                        printf("\n            ZEROS ARE NOT ALLOWED IN THE \
PRINCIPLE DIAGONAL.\n            YOU MUST ENTER ANOTHER ANALOGOUS ROW.\n\
            THERE WAS A DISCREPANCY IN ROW %d  ELEMENT %d \n\n",alpha+1,alpha+1);
                        beta = -1;                     
                  }
		}
		printf("\n");
	}
    	printf("  NOW INPUT COLUMN OF ANSWERS\n");
	for( beta=0; beta<size; beta++)
	{
                printf("B(%d)\n",beta+1);
		b[beta]=atof(gets(buffer));
	}
	for(gamma=0; gamma<size; gamma++)
	{
		for(beta=gamma; beta<size; beta++)
		{
                    if(  (store = a[beta][gamma]) != 0.0 )
                    {
                        for(alpha=gamma; alpha<size; alpha++)
                        {
			        a[beta][alpha] /= store;
                        }
                        b[beta] /= store;
                    }
                }
                for(beta=gamma+1; beta < size; beta++)
                {
                    if( a[beta][gamma] != 0.0 )
                    {
                         for(alpha=gamma; alpha<size; alpha++)
                         {
                                 a[beta][alpha] -=  a[gamma][alpha];
                         }
                         b[beta] -= b[gamma];
                    }
                 }
         }
         for(alpha=0; alpha<size; alpha++)
         {
                if( a[alpha][alpha] == 0.0  )
                {
                              printf("\n\nTHERE IS NO UNIQUE SOLUTION\n\n");
                              getch();
                              exit(1);
                }
         }
         printf("\n\n          THE SOLUTIONS ARE THE FOLLOWING:\n");
         printf("\nX[%d] = (%g)", size, b[size-1]);
         for(gamma=size-2; gamma >= 0;gamma--)
         {
                store=0;
                for(beta=size-1 ; beta > gamma;  beta--)
                {
                        store += a[gamma][beta]*b[beta];
                }
                b[gamma] -= store;
                printf("\nX[%d] = (%g)",gamma+1,b[gamma]);
        }
getch();
}