Method of Gauss

[Sega]

Hello
Help to correct the program, defines roots correctly, but in a wrong order

#include <iostream>
#include <cmath>


using namespace std;

void Gauss(double *a, double *b, double *x,int n) {
 int i,j,k,t;
 double kof,s;
 double temp;
 for (i=n-1; i>0; --i) 
 {
  for (t=i, j=i-1; j>=0; --j) 
  {
   if (fabs(a[i*n+t])<fabs(a[i*n+j]))
   {
    t=j;
   }
  }
  if (a[i*n+t]==0.0)
  {
   return;
  }
  if (t!=i) 
  {
   for (k=n-1; k>=0; --k) 
   {
    temp=a[k*n+t];
    a[k*n+t]=a[k*n+i];
    a[k*n+i]=temp;
   }
  }
  for (j=i-1; j>=0; --j) 
  {
   kof=a[i+j*n]/a[i*n+i]; // kof=a[j][i]/a[i][i];
   for (a[i+j*n]=0.0, b[j]-=b[i]*kof, k=i-1; k>=0; --k) 
   {
    a[k+j*n]-=a[k+i*n]*kof; // a[k][j]-=a[k][i]*kof
   }
  }
 }
 x=new double [n];
 if (x)
 {
  for (i=0; i<n; ++i)
  {
   for (s=0.0, j=i-1; j>=0; --j)
   {
    s+=a[j+i*n]*x[j]; //s+=a[j][i]*x[j]
   }
   x[i]=(b[i]-s)/a[i*n+i]; // x[i]=(b[i]-s)/a[i][i];
   //cout << x[i] << "\n";
  }
 }
 cout << "\n";
 for (i=0; i<n; ++i)
cout << "x " << x[i] << endl;
}


main()
{

      int n = 6;
     double gauss2[6] ={1,5,3,7,6,3};
      double M[36]={-3, 2, 1,2, 3, 1,5, 3, 3, -1, 3, 4,0, 80,46, 34, 3, 4,6, 7, 3, 6, 6,7,57, 6, 5, 5, 3, 67,1, 55, 5, 7, 3, 7 };
        
      double *y = new double[n];

	/*  for(int i=0; i<n; i++)
		{
			for(int j=0; j<n; j++)
				{
					//cin >> M[i+j*n];
					 M[i+j*n] = rand()/100;
//cout << "gauss1["<< i << "][" << j << "]=";
//cin >> gauss1[i][j];
				}
		}
*/
for(int i=0; i<n; i++)
		{
			for(int j=0; j<n; j++)
				{
					 cout << M[i*n+j] << "  ";
				}
				cout << gauss2[i] << endl;
		}	
      Gauss(M,gauss2,y,n);
       cin.get();
}

My answer: 0.63, -0.12, 0.0249, 1.16, -0.49, -0.0558
Right answer: 0.63, 0.06, 0.02, -0.12, 1.16, -0.49

[WingedPanther]

Why not just sort your array before outputting it? Gauss's method is not guaranteed to generate roots in any particular order.

[Sega]

Gauss's method is not guaranteed to generate roots in any particular order.

Why does not guaranteed? In fact, after finding the roots, of their substitute in a certain order, and not in an arbitrary, is not it?

[Sega]

If Substituting: 0.63, -0.12, 0.0249, 1.16, -0.49, -0.0558 , then the right decision not succeed
so that the sequence of roots is important

[WingedPanther]

Again, why not just sort the array before printing it?