#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int main()
{
int a[5][5],b[5],n,i,j,flag=1,key=0;
char c;
float e,sum,xo[10],x1[10],s;
setbuf(stdout,NULL);
printf("This program illustrates Gauss Jacobi Method in C :\n");
printf("Enter the dimension of the coefficient matrix A:");
scanf("%d",&n);
printf("Enter the %d elements of the coefficient matrix A:",n*n);
for(i=0;i<n;i++)
for(j=0;j<n;j++)
scanf("%d",&a[i][j]);
printf("Enter the elements of the constant matrix B:");
for(i=0;i<n;i++)
scanf("%d",&b[i]);
printf("The given system of linear equations is\n");
for(i=0;i<n;i++)
{
for(j=0;j<n;j++)
{
if((j==0 || j==1 ) && (a[i][j+1]>0))
c='+';
else if(j==2)
c='=';
printf("%dx%d\t%c",a[i][j],j+1,c);
}
printf("%d",b[i]);
printf("\n");
}
for(i=0;i<n;i++)
{
for(j=0;j<n;j++)
{
if(i!=j)
s=s+a[i][j];
}
if(fabs(a[i][i])<fabs(s))
{
flag=0;
break;
}
}
if(flag==0)
{
printf("Error!The given system of linear equations is not diagonally dominant.");
exit(0);
}
else
{
printf("The given system of linear equations is diagonally dominant.a\n");
printf("Enter the initial approximate solution to the given system:");
for(i=0;i<n;i++)
{
scanf("%f\t",&xo[i]);
}
for(i=0;i<n;i++)
{
printf("x%d=%f\t",i+1,xo[i]);
}
printf("Enter the allowed error:");
scanf("%f",&e);
do{
for(i=0;i<n;i++)
{
sum=b[i];
for(j=0;j<n;j++)
{
if(j!=i)
sum=sum-a[i][j]*xo[j];
}
x1[i]=sum/a[i][i];
if(fabs(x1[i]-xo[i])<e)
{
key=key+1;
xo[i]=x1[i];
}
}
}while(key<n);
}
if(key==n)
for(i=0;i<n;i++)
printf("%f\t",xo[i]);
}