In-polygon test

In-polygon.cpp

bool in_polygon(const point &p, point ps[], int len)
{
	int i, j = len - 1;
	bool oddNodes = false;

	for (i = 0; i < len; i++) {
		if ((ps[i].y < p.y && ps[j].y >= p.y
			|| ps[j].y < p.y && ps[i].y >= p.y)
			&& (ps[i].x <= p.x || ps[j].x <= p.x))
		{
			oddNodes ^= (ps[i].x + (p.y - ps[i].y) / (ps[j].y - ps[i].y) * (ps[j].x - ps[i].x) < p.x);
		}
		j = i;
	}

	return oddNodes;
}