Gaussian_elimination.c

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

#define   SIZE   10

int main()
{
	 float a[SIZE][SIZE], x[SIZE], ratio;
	 int i,j,k,n;
	

	 printf("Enter number of unknowns: ");
	 scanf("%d", &n);
	 for(i=1;i<=n;i++)
	 {
		  for(j=1;j<=n+1;j++)
		  {
			   printf("a[%d][%d] = ",i,j);
			   scanf("%f", &a[i][j]);
		  }
	 }
	 for(i=1;i<=n-1;i++)
	 {
		//   if(a[i][i] == 0.0)
		//   {
		// 	   printf("Mathematical Error!");
		// 	   exit(0);
		//   }
		for(j=i+1;j<=n;j++)
		{
			
			ratio = a[j][i]/a[i][i];
			
			for(k=1;k<=n+1;k++)
			{
				a[j][k] = a[j][k] - ratio*a[i][k];
			}
		}
	 }
	 x[n] = a[n][n+1]/a[n][n];
	
	 for(i=n-1;i>=1;i--)
	 {
		  x[i] = a[i][n+1];
		  for(j=i+1;j<=n;j++)
		  {
		  		x[i] = x[i] - a[i][j]*x[j];
		  }
		  x[i] = x[i]/a[i][i];
	 }
	 printf("\nSolution:\n");
	 for(i=1;i<=n;i++)
	 {
	  	printf("x[%d] = %0.3f\n",i, x[i]);
	 }
	 getch();
	 return(0);
}