Project Euler > Problem 102 > Triangle containment (Java Solution)

Problem:

Three distinct points are plotted at random on a Cartesian plane, for which -1000 [≤] x, y [≤] 1000, such that a triangle is formed.

Consider the following two triangles:

A(-340,495), B(-153,-910), C(835,-947)

X(-175,41), Y(-421,-714), Z(574,-645)

It can be verified that triangle ABC contains the origin, whereas triangle XYZ does not.

Using triangles.txt (right click and 'Save Link/Target As...'), a 27K text file containing the co-ordinates of one thousand "random" triangles, find the number of triangles for which the interior contains the origin.

NOTE: The first two examples in the file represent the triangles in the example given above.

Solution:

4613732

Code:
The solution may include methods that will be found here: Library.java .

public interface EulerSolution{

public String run();

}

/* 
 * Solution to Project Euler problem 2
 * By Nayuki Minase
 * 
 * http://nayuki.eigenstate.org/page/project-euler-solutions
 * https://github.com/nayuki/Project-Euler-solutions
 */


public final class p002 implements EulerSolution {
	
	public static void main(String[] args) {
		System.out.println(new p002().run());
	}
	
	
	public String run() {
		int sum = 0;
		for (int i = 0; ; i++) {
			int fib = fibonacci(i);
			if (fib > 4000000)
				break;
			if (fib % 2 == 0)
				sum += fib;
		}
		return Integer.toString(sum);
	}
	
	
	private static int fibonacci(int x) {
		if (x < 0 || x > 46)
			throw new IllegalArgumentException();
		int a = 0;
		int b = 1;
		for (int i = 0; i < x; i++) {
			int c = a + b;
			a = b;
			b = c;
		}
		return a;
	}
	
}