UVa 378 - Intersecting Lines

// UVa 378 - Intersecting Lines

#include <iostream>
#include <cmath>
#include <stdio.h>
using namespace std;

struct point {
	double x, y;
};

struct line {
	double a, b, c;
};

line points_to_line(point p, point q) {
	line l;
	l.a = p.y - q.y;
	l.b = q.x - p.x;
	l.c = -l.a * p.x - l.b * p.y;
	return l;
}

bool are_parallel(line l1, line l2) {
	return l1.b * l2.a == l2.b * l1.a;
}

point intersection(line l1, line l2) {
	point p;
	p.y = (l2.c * l1.a - l1.c * l2.a) / (l1.b * l2.a - l2.b * l1.a);
	p.x = (l2.c * l1.b - l1.c * l2.b) / (l1.a * l2.b - l2.a * l1.b);
	return p;
}

bool are_same(line l1, line l2) {
	if ((l1.b == 0) ^ (l2.b == 0))
		return false;
	else if (l1.b == 0 && l2.b == 0)
		return l1.c / l1.a == l2.c / l2.a;
	else
		return l1.a / l1.b == l2.a / l2.b && l1.c / l1.a == l2.c / l2.a;
}

int main() {
	cout << "INTERSECTING LINES OUTPUT\n";
	int n;
	for (cin >> n; n; n--) {
		point p1, p2, p3, p4;
		cin >> p1.x >> p1.y >> p2.x >> p2.y >> p3.x >> p3.y >> p4.x >> p4.y;
		line l1 = points_to_line(p1, p2);
		line l2 = points_to_line(p3, p4);
		if (are_same(l1, l2))
			cout << "LINE" << endl;
		else if (are_parallel(l1, l2)) {
			cout << "NONE" << endl;
		} else {
			point inter = intersection(l1, l2);
			printf("POINT %.2f %.2f\n", inter.x, inter.y);
		}
	}
	cout << "END OF OUTPUT\n";
	return 0;
}