/* SOLVING EQUATIONS USING GAUSS SEIDEL ITERATIONS */

# include <stdio.h>
# include <conio.h>
void main()
{
	float a[10][10]/* coefficients */,x[10]/* variables */,v[10][10],b[10]/* constants */;
	int i,j,k=0,m,it,var;
	float n=0.0,p;
	printf("\n\tNOTE: SOLUTION EXISTS ONLY IF GAUSS-SEIDEL ITERATION CONVERGES\n");
	printf("\nENTER THE EQUATIONS IN THE FORM ax + by + cz = D");
	printf("\nHOW MANY VARIABLES:\t");
	scanf("%d",&var);
	for(i=0;i<var;++i)
	{
		for(j=0;j<var;++j)
			scanf("%f",&a[i][j]);
		scanf("%f",&b[i]);
	}
	for(j=0;j<var;++j)
	{
		if(a[j][j] == 0)
			++k;
	}
	if(k == var)
		printf("\n*****     error:cannot solve using gauss seidel method     *****");
	else
	{
	printf("\nHOW MANY ITERATIONS SHOULD BE PERFORMED:\t");
	scanf("%d",&it);
	printf("\nENTER INITIAL APPROXIMATIONS:-");
	for(i=0;i<var;++i)
	{
		printf("\n x[%d] = ",i+1);
		scanf("%f",&x[i]);
	}
	for(j=0;j<var;++j)
	{
		for(k=0;k<var;++k)
		{
			if( j != k )
				v[j][k] = -(a[j][k]/a[j][j]);
		}
		b[j] = b[j]/a[j][j];
	}
	for(m=0;m<it;++m)
	{
		printf("\n");
		for(j=0;j<var;++j)
		{
			n = 0.0;
			for(k=0;k<var;++k)
			{
				if(j != k)
				{
					p = v[j][k]*x[k];
					n = n + p;
				}
			}
			x[j] = n + b[j];
			printf("\t%.3f",x[j]);
			
		}
	}
	getch();
	}
}