Factor a trinomial in C++

factortrinomial.cpp

//Paul Booth
//June 01, 2009
//Programming 3 final program
//Trinomial factoring program
//inputs a trinomial, displays factored form


#include <iostream>
#include <windows.h>

using namespace std; 

int bestfactor(int n);
void getInput();
void displayOutput();
void reduce (int &num1, int &num2);
void displayGraph();
void setTextColor(int fg,int bg);
void cycleColors();

int a,b,c,//trinomial parameters
term1,term2,coef1, coef2, //factored answer parameters
fgindex=2, bgindex=10;//color code numbers for (f)ore(g)round and (b)ack(g)round-will change

//graph settings2
const int graphWidth=79, graphHeight=40;
const double errorRange=4;//thickness of graph
const char hit=char(219), //char of function
	miss=' ';//char of background 
const int graphfg=13,//color of funct.
	 graphbg=0;//color of background

void getInput(){//gets input
	cycleColors();
	cout<<"trinomial of form Ax^2+Bx+C\n";
	cycleColors();
	cout << "enter in A (nonzero):" ;
	cin>>a;
	cycleColors();
	cout << "enter in B:" ;
	cin>>b;
	cycleColors();
	cout << "enter in C:" ;
	cin>>c;
	cycleColors();
}
void displayOutput(){//displays answer
cycleColors();
	cout<<"(";
	if (coef1!=1) 
		cout<<coef1;
	cout<<"X"<<((term1>=0)?"+":"")<<term1<<")";
	cout<<"(";
	if(coef2!=1) 
		cout<<coef2;
	cout<<"X"<<((term2>=0)?"+":"")<<term2<<")"<<endl;
	displayGraph();

}
void displayGraph(){//displays graph centered at vertex
setTextColor(graphfg,graphbg);
	for(int y=graphHeight/2;y>=-graphHeight/2;y--){
		for(int x=-b/(2*a)-graphWidth/2;x<=-b/(2*a)+graphWidth/2;x++){
			if(x==0&&y==0){
				cout<<char(197);
			}
			else if (x==0){
				cout<<char(179);
				}
				else if(y==0){
					 cout<<char(196);
					}
					else
						if (abs(x*x*a+b*x+c-y)>errorRange){
							cout<<miss;
							}
						else {
							cout<<hit;
							}
			
		}
		cout<<endl;
	}
	cycleColors();



}
int main( void )
{
	getInput();
	//input as ax^2+bx+c
	//put answer in ((coef1)x+term1)((coef2)x+term2) form
	coef2=coef1=a;
	cout<<a<<endl;
	term1=bestfactor(a*c);//first factor
	cout<<term1<<endl;
	if(term1!=0)
		term2=(a*c)/term1;//second factor
	else{
		term2=b;
		coef1=1;
		}
	
	
	reduce(coef1,term1);//make sure it can't be simplified
	reduce(coef2,term2);
	displayOutput();
	return 0;
}
void reduce (int &num1, int &num2){//reduces a pair of numbers -removes common factors
	for(int i=2;i<=min(abs(num1),abs(num2));i++){
		if((num1%i==0)&&(num2%i==0))
		{
		num1/=i; num2/=i;
		}
	}


}
int bestfactor(int n){//finds factors of n that add to b in equation- returns first one
	for(int i=1;i<=abs(n);i++){
		if (n%i==0){
				int comp=n/i;
				if (comp+i==b)
					return i;
		}
	}
	for(int i=-1;i>=-abs(n);i--){
		if (n%i==0){
				int comp=n/i;
				if (comp+i==b)
					return i;
		}
	}
	return 0;

}
void setTextColor(int fg,int bg){//sets forground and background text colors
	HANDLE hconsole= GetStdHandle(STD_OUTPUT_HANDLE);
	SetConsoleTextAttribute(hconsole, fg|bg<<4);

}
void cycleColors(){//changes forground and background text colors
	fgindex++; bgindex++;
	setTextColor(fgindex,bgindex);

}