def convex_hull(
points: List[Union[Tuple[float, float], List[float],
Point]]) -> List[Point]:
"""For given list of points return its convex hull"""
_at = (tuple, list, Point) # allowed types
points = [Point.from_iter(i) for i in points
if type(i) in _at] # converts to points
points.sort(key=lambda p: p.x) # sort points by x axis
l_upper = [points[0], points[1]] # add two leftmost points to L(upper) set
for i in range(2, len(points)): # for all other points
l_upper.append(points[i]) # add the next point to L set
# test the last three points in L
while len(l_upper) > 2 and not _is_right_turn(l_upper[-3], l_upper[-2],
l_upper[-1]):
# remove the middle of tested three points when they don't make right turn
l_upper.pop(-2)
l_lower = [points[-1],
points[-2]] # L(lower) begins with the two rightmost points
# apply the same algorithm for reversed values
for i in reversed(range(len(points) - 3)):
l_lower.append(points[i])
while len(l_lower) > 2 and not _is_right_turn(l_lower[-3], l_lower[-2],
l_lower[-1]):
l_lower.pop(-2)
# remove the first from lower L as it is the same as the last in the upper L
# append lower to upper L
return l_upper + l_lower[1:]
def find_intersections_slow(line_segments: List[LineSegment]) -> List[Point]:
result = set()
for i in range(len(line_segments)):
for ls in line_segments[i + 1:]:
intersection = LineSegment.intersection(ls, line_segments[i])
if intersection:
result.add((intersection.x, intersection.y))
return [Point.from_iter(i) for i in result]
print(status)
print()
del q[event_point.key]
step += 1
plt_line_segments(line_segments)
plt.scatter([p.x for p in result], [p.y for p in result], c='k')
plt.title("Sweep line algorithm")
plt.axis([-r, r, -r, r])
if legend:
plt.legend(fancybox=True, framealpha=0.3)
plt.show()
print("=============\nSLOW ALGORITHM")
intersections = [Point.from_iter(i) for i in intersections]
print("Number of intersections:", len(intersections))
print(intersections)
print("\nSWEEP LINE ALGORITHM")
print("Number of intersections:", len(result))
print(result)
print("\nSWEEP LINE ALGORITHM (SOURCE)")
fi = find_intersections(line_segments)
print("Number of intersections:", len(fi))
print(fi)
# the current result and result from the slow algorithm and result from imported algorithm
assert sorted(result) == sorted(intersections) == sorted(fi)
