Mirror Reflection leetcode code example

Example: Mirror Reflection leetcode

class Solution {
    double EPS = 1e-6;

    public int mirrorReflection(int p, int q) {
        double x = 0, y = 0;
        double rx = p, ry = q;    

        // While it hasn't reached a receptor,...
        while (!( close(x, p) && (close(y, 0) || close(y, p))
                  || close(x, 0) && close (y, p) )) {
            // Want smallest t so that some x + rx, y + ry is 0 or p
            // x + rxt = 0, then t = -x/rx etc.
            double t = 1e9;
            if ((-x / rx) > EPS) t = Math.min(t, -x / rx);
            if ((-y / ry) > EPS) t = Math.min(t, -y / ry);
            if (((p-x) / rx) > EPS) t = Math.min(t, (p-x) / rx);
            if (((p-y) / ry) > EPS) t = Math.min(t, (p-y) / ry);

            x += rx * t;
            y += ry * t;

            if (close(x, p) || close(x, 0)) rx *= -1;
            if (close(y, p) || close(y, 0)) ry *= -1;
        }

        if (close(x, p) && close(y, p)) return 1;
        return close(x, p) ? 0 : 2;
    }

    public boolean close(double x, double y) {
        return Math.abs(x - y) < EPS;
    }
}