Полностью сделал задачу 6 на вычислительную геометрию
This commit is contained in:
parent
a08f95aef8
commit
3efd67c703
15 changed files with 570 additions and 60 deletions
175
ComputationalGeometry/6Ex/PythonVersion/main.py
Normal file
175
ComputationalGeometry/6Ex/PythonVersion/main.py
Normal file
|
@ -0,0 +1,175 @@
|
|||
# Python3 program to find the minimum enclosing
|
||||
# circle for N integer points in a 2-D plane
|
||||
from math import sqrt
|
||||
from random import randint, shuffle
|
||||
|
||||
# Defining infinity
|
||||
INF = 1e18
|
||||
MAX_POINT_COORD = 100
|
||||
|
||||
|
||||
# Structure to represent a 2D point
|
||||
class Point:
|
||||
def __init__(self, X=0, Y=0) -> None:
|
||||
self.X = X
|
||||
self.Y = Y
|
||||
|
||||
|
||||
# Structure to represent a 2D circle
|
||||
class Circle:
|
||||
def __init__(self, c=Point(), r=0) -> None:
|
||||
self.C = c
|
||||
self.R = r
|
||||
|
||||
def print(self) -> None:
|
||||
print(f"(x - {self.C.X})^2 + (y - {self.C.Y})^2 = {self.R}^2")
|
||||
|
||||
|
||||
# Function to return the euclidean distance
|
||||
# between two points
|
||||
def dist(a, b):
|
||||
return sqrt(pow(a.X - b.X, 2)
|
||||
+ pow(a.Y - b.Y, 2))
|
||||
|
||||
|
||||
# Function to check whether a point lies inside
|
||||
# or on the boundaries of the circle
|
||||
def is_inside(c, p):
|
||||
return dist(c.C, p) <= c.R
|
||||
|
||||
|
||||
# The following two functions are used
|
||||
# To find the equation of the circle when
|
||||
# three points are given.
|
||||
|
||||
# Helper method to get a circle defined by 3 points
|
||||
def get_circle_center(bx, by,
|
||||
cx, cy):
|
||||
B = bx * bx + by * by
|
||||
C = cx * cx + cy * cy
|
||||
D = bx * cy - by * cx
|
||||
return Point((cy * B - by * C) / (2 * D),
|
||||
(bx * C - cx * B) / (2 * D))
|
||||
|
||||
|
||||
# Function to return the smallest circle
|
||||
# that intersects 2 points
|
||||
def circle_from1(A, B):
|
||||
# Set the center to be the midpoint of A and B
|
||||
C = Point((A.X + B.X) / 2.0, (A.Y + B.Y) / 2.0)
|
||||
|
||||
# Set the radius to be half the distance AB
|
||||
return Circle(C, dist(A, B) / 2.0)
|
||||
|
||||
|
||||
# Function to return a unique circle that
|
||||
# intersects three points
|
||||
def circle_from2(A, B, C):
|
||||
I = get_circle_center(B.X - A.X, B.Y - A.Y,
|
||||
C.X - A.X, C.Y - A.Y)
|
||||
|
||||
I.X += A.X
|
||||
I.Y += A.Y
|
||||
return Circle(I, dist(I, A))
|
||||
|
||||
|
||||
# Function to check whether a circle
|
||||
# encloses the given points
|
||||
def is_valid_circle(c, P):
|
||||
# Iterating through all the points
|
||||
# to check whether the points
|
||||
# lie inside the circle or not
|
||||
for p in P:
|
||||
if (not is_inside(c, p)):
|
||||
return False
|
||||
return True
|
||||
|
||||
|
||||
# Function to return the minimum enclosing
|
||||
# circle for N <= 3
|
||||
def min_circle_trivial(P):
|
||||
assert (len(P) <= 3)
|
||||
if not P:
|
||||
return Circle()
|
||||
|
||||
elif (len(P) == 1):
|
||||
return Circle(P[0], 0)
|
||||
|
||||
elif (len(P) == 2):
|
||||
return circle_from1(P[0], P[1])
|
||||
|
||||
# To check if MEC can be determined
|
||||
# by 2 points only
|
||||
for i in range(3):
|
||||
for j in range(i + 1, 3):
|
||||
|
||||
c = circle_from1(P[i], P[j])
|
||||
if (is_valid_circle(c, P)):
|
||||
return c
|
||||
|
||||
return circle_from2(P[0], P[1], P[2])
|
||||
|
||||
|
||||
# Returns the MEC using Welzl's algorithm
|
||||
# Takes a set of input points P and a set R
|
||||
# points on the circle boundary.
|
||||
# n represents the number of points in P
|
||||
# that are not yet processed.
|
||||
def welzl_helper(P, R, n):
|
||||
# Base case when all points processed or |R| = 3
|
||||
if (n == 0 or len(R) == 3):
|
||||
return min_circle_trivial(R)
|
||||
|
||||
# Pick a random point randomly
|
||||
idx = randint(0, n - 1)
|
||||
p = P[idx]
|
||||
|
||||
# Put the picked point at the end of P
|
||||
# since it's more efficient than
|
||||
# deleting from the middle of the vector
|
||||
P[idx], P[n - 1] = P[n - 1], P[idx]
|
||||
|
||||
# Get the MEC circle d from the
|
||||
# set of points P - :p
|
||||
d = welzl_helper(P, R.copy(), n - 1)
|
||||
|
||||
# If d contains p, return d
|
||||
if (is_inside(d, p)):
|
||||
return d
|
||||
|
||||
# Otherwise, must be on the boundary of the MEC
|
||||
R.append(p)
|
||||
|
||||
# Return the MEC for P - :p and R U :p
|
||||
return welzl_helper(P, R.copy(), n - 1)
|
||||
|
||||
|
||||
def welzl(P):
|
||||
P_copy = P.copy()
|
||||
shuffle(P_copy)
|
||||
return welzl_helper(P_copy, [], len(P_copy))
|
||||
|
||||
|
||||
def generate(num: int) -> list[Point]:
|
||||
data: list[Point] = list()
|
||||
|
||||
for i in range(num):
|
||||
data.append(Point(randint(-MAX_POINT_COORD, MAX_POINT_COORD), randint(-MAX_POINT_COORD, MAX_POINT_COORD)))
|
||||
|
||||
return data
|
||||
|
||||
|
||||
def printPoints(data: list[Point]) -> None:
|
||||
for i in range(len(data)):
|
||||
print(f"{chr(i + 65)} = ({data[i].X}, {data[i].Y})")
|
||||
|
||||
|
||||
# Driver code
|
||||
if __name__ == '__main__':
|
||||
num = int(input("Enter number of points: "))
|
||||
data = generate(num)
|
||||
|
||||
printPoints(data)
|
||||
|
||||
mec = welzl(data)
|
||||
mec.print()
|
Loading…
Add table
Add a link
Reference in a new issue