(useless) furthestPoints (rotating calipers)

upd : now all in Geometry..

std::pair<Point, Point> furthestPoints(const std::vector<Point>& pts) {
  assert(!pts.empty());
  auto hull = getConvexHull(pts);
  int n = hull.size();
  G max_dist = -1;
  std::pair<Point, Point> res;
  for (int i = 0, j = 0; i < n; ++i) {
    if (auto d = dist2(hull[i], hull[j]); max_dist < d) {
      max_dist = d;
      res = {hull[i], hull[j]};
    }
    while (ccw(hull[i], hull[(i + 1) % n], hull[(i + 1) % n] + hull[(j + 1) % n] - hull[j]) >= 0) {
      j = (j + 1) % n;
      if (auto d = dist2(hull[i], hull[j]); max_dist < d) {
        max_dist = d;
        res = {hull[i], hull[j]};
      }
      if (i == j) {
        break;
      }
    }
  }
  return res;
}