#include<stdio.h>
#include<conio.h>
#define EQ 10

float truncate(float, int);
void show(float eq[EQ][EQ+1], int);
void main(void)
{
float eq[EQ][EQ+1], var[EQ];
float sum;  int n;
clrscr();
do	{
	printf("Enter the no. of variables(Less than %d) :",EQ);
	n=getche();
	n-=0x30;
	}while(n<1 || n>EQ);

for(int j=0; j<n; j++)  // enter eqn.
	{
	printf("\nEnter the Eqn. no: %d\n", j+1);
	printf("\tEnter COEFFICIENTS: ");
	for(int i=0; i<n; i++)
		{ scanf("%f",&eq[j][i]); }
	printf("\tEnter CONSTANT: ");
	scanf("%f",&eq[j][i]);
	}

for(int i=0; i<n; i++)  // i is COL
	{
	float factor=0.0;
	for(int j=i+1; j<n; j++) //j is ROW
		{
		factor=eq[j][i] / eq[i][i];
		for(int col=i; col<n+1; col++)
			{
			eq[j][col] = eq[j][col] - factor*eq[i][col];
			if(eq[j][col]<1E-6 && eq[j][col]>-1E-6)
				eq[j][col] = truncate(eq[j][col], 6);
			}
		}
	}
printf("\n\nThe Upper Triangular Matrix Is: ");
show(eq, n);	puts("\n\n");
while(!kbhit() );	//do nothing while.
getch();

//	BLOCK TO FIND OUT THE VARIABLE START
	{
	var[n-1]=eq[n-1][n] / eq[n-1][n-1];
	for(int it=0; it<n; it++)
		{
		sum=0.0;
		int j = n-1-it;
		for(int i=j+1; i<n; i++)
			{
			sum+=var[i]*eq[j][i];
			}
		var[j] = (eq[j][n] - sum) / eq[j][j];
		}
	}
//	BLOCK END; VARS. FOUND.

for(int z=0; z<n; z++) // show result
	{
	printf("Variable #%.2d is %6.4f\n",z+1, var[z]);
	}
while(!kbhit()); z=getch();
}

void show(float eq[EQ][EQ+1], int n)
{
printf("\n");
for(int j=0; j<n; j++)
	{
	for(int i=0; i<n+1; i++)
		{
		printf("%5.3f\t",eq[j][i]);
		}
	printf("\n");
	}
}

long int pow(int b, int i)
{
long int l=1L;
for(int j=0;j<i;j++)
	{
	l=l*b;
	}
return l;
}
float truncate(float f, int i)
{
float tmp; int t;
f=f*pow(10,i);
t=(int)f;
tmp=(float)t;
tmp=tmp/pow(10, i);
return tmp;
}