//Compiler directives
#include<stdio.h>
#include<iostream.h>
#include<conio.h>
#include<string.h>
#include<ctype.h>
#include<math.h>
#include<stdlib.h>
#include<iomanip.h>
#include<dos.h>
#include<graphics.h>
#include<fstream.h>
#include<process.h>
#include<time.h>

int diff1[20],numb[20],diff2[20];

void neither()
{
cout<<endl;
sound(1000);
delay(500);
nosound();
sleep;
textcolor(GREEN);
cout<<"This is not a Linear nor a Quadratic! Get your numbers right!"<<endl;
cout<<"__________________________________________________________"<<endl<<endl;
getch();
exit(1);
}

void diff()
{
cout<<"The first difference is:"<<endl;
cout<<"________________________"<<endl;
cout<<endl;
for(int c=2;c<=4;c++)
{
	diff1[c - 1] = numb[c] - numb[c - 1];
	cout<<diff1[c - 1]<<endl;
}
}

void quad()
{
cout<<endl;
sleep(1);
cout<<"This is a Quadratic equation. The Quadratic equation is:"<<endl<<endl;
textcolor(GREEN);
cout<<"Y = "<<diff2[1]/2<<"x^2 + "<<diff1[1]-diff2[1]/2<<" x + "<<numb[1]<<endl;
cout<<endl;
getch();
exit(1);
}

void diff_2()
{
cout<<endl<<"The second difference is"<<endl;
cout<<"_________________________"<<endl<<endl;
for(int d=2;d<=3;d++)
{
	diff2[d-1] = diff1[d]-diff1[d - 1];
	cout<<diff2[d - 1]<<endl;
}
if(!(diff2[1] == diff2[2]))
	neither();
else
	quad();
exit(1);
}

void linear()
{
for(int a=2;a<=3;a++)
{
	if(!(diff1[a]==diff1[a - 1]))
		diff_2();
}
cout<<endl;
sleep(1);
cout<<"This is a Linear equation. The Linear equation is: "<<endl;
textcolor(GREEN);
cout<<"Y ="<<diff1[2]<<"X + "<<numb[1];
getch();
exit(1);
}

void main()
{
clrscr();
cout<<" <<WELCOME TO THE LINEAR/QUADRATIC PROGRAM!!>>"<<endl;
cout<<" _____________________________________________"<<endl;
cout<<endl<<endl<<endl<<endl;
cout<<" Instructions:"<<endl;
cout<<" _____________"<<endl;
cout<<endl;
cout<<" 1) You are to input four numbers of your choice."<<endl;
cout<<" 2) Then the program will determine if the number sequence"<<endl;
cout<<"    is a possible solution for a Linear or Quadratic equation."<<endl;
cout<<" 3) It will display the results."<<endl;
cout<<" __________________________________________________________________________"<<endl;
cout<<endl;

for(int a=1;a<=4;a++)
{
	cout<<endl<<"Input number: "; cin>>numb[a];
}

clrscr();
cout<<"The numbers are:"<<endl;
cout<<"________________"<<endl;
for(int b=1;b<=4;b++)
	cout<<numb[b]<<endl;

diff();
linear();
diff_2();
getch();
}