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Update closest_pair_of_points.py ()

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Harshil 2019-08-06 21:31:03 +02:00 committed by Christian Clauss
parent d21b4cfb48
commit 762482dc40
1 changed files with 57 additions and 50 deletions

43
divide_and_conquer/closest_pair_of_points.py

@ -19,30 +19,26 @@ min(closest_pair_dis, closest_in_strip) would be the final answer.
Time complexity: O(n * log n) Time complexity: O(n * log n)
""" """
"""
doctests
>>> euclidean_distance_sqr([1,2],[2,4])
5
>>> dis_between_closest_pair([[1,2],[2,4],[5,7],[8,9],[11,0]],5)
5
>>> dis_between_closest_in_strip([[1,2],[2,4],[5,7],[8,9],[11,0]],5)
85
>>> points = [(2, 3), (12, 30), (40, 50), (5, 1), (12, 10), (3, 4)]
>>> print("Distance:", closest_pair_of_points(points, len(points)))
"Distance: 1.4142135623730951"
"""
def euclidean_distance_sqr(point1, point2): def euclidean_distance_sqr(point1, point2):
"""
>>> euclidean_distance_sqr([1,2],[2,4])
5
"""
return (point1[0] - point2[0]) ** 2 + (point1[1] - point2[1]) ** 2 return (point1[0] - point2[0]) ** 2 + (point1[1] - point2[1]) ** 2
def column_based_sort(array, column = 0): def column_based_sort(array, column = 0):
"""
>>> column_based_sort([(5, 1), (4, 2), (3, 0)], 1)
[(3, 0), (5, 1), (4, 2)]
"""
return sorted(array, key = lambda x: x[column]) return sorted(array, key = lambda x: x[column])
def dis_between_closest_pair(points, points_counts, min_dis = float("inf")): def dis_between_closest_pair(points, points_counts, min_dis = float("inf")):
""" brute force approach to find distance between closest pair points """
brute force approach to find distance between closest pair points
Parameters : Parameters :
points, points_count, min_dis (list(tuple(int, int)), int, int) points, points_count, min_dis (list(tuple(int, int)), int, int)
@ -50,6 +46,9 @@ def dis_between_closest_pair(points, points_counts, min_dis = float("inf")):
Returns : Returns :
min_dis (float): distance between closest pair of points min_dis (float): distance between closest pair of points
>>> dis_between_closest_pair([[1,2],[2,4],[5,7],[8,9],[11,0]],5)
5
""" """
for i in range(points_counts - 1): for i in range(points_counts - 1):
@ -61,7 +60,8 @@ def dis_between_closest_pair(points, points_counts, min_dis = float("inf")):
def dis_between_closest_in_strip(points, points_counts, min_dis = float("inf")): def dis_between_closest_in_strip(points, points_counts, min_dis = float("inf")):
""" closest pair of points in strip """
closest pair of points in strip
Parameters : Parameters :
points, points_count, min_dis (list(tuple(int, int)), int, int) points, points_count, min_dis (list(tuple(int, int)), int, int)
@ -69,6 +69,8 @@ def dis_between_closest_in_strip(points, points_counts, min_dis = float("inf")):
Returns : Returns :
min_dis (float): distance btw closest pair of points in the strip (< min_dis) min_dis (float): distance btw closest pair of points in the strip (< min_dis)
>>> dis_between_closest_in_strip([[1,2],[2,4],[5,7],[8,9],[11,0]],5)
85
""" """
for i in range(min(6, points_counts - 1), points_counts): for i in range(min(6, points_counts - 1), points_counts):
@ -88,6 +90,8 @@ def closest_pair_of_points_sqr(points_sorted_on_x, points_sorted_on_y, points_co
Returns : Returns :
(float): distance btw closest pair of points (float): distance btw closest pair of points
>>> closest_pair_of_points_sqr([(1, 2), (3, 4)], [(5, 6), (7, 8)], 2)
8
""" """
# base case # base case
@ -104,7 +108,8 @@ def closest_pair_of_points_sqr(points_sorted_on_x, points_sorted_on_y, points_co
points_counts - mid) points_counts - mid)
closest_pair_dis = min(closest_in_left, closest_in_right) closest_pair_dis = min(closest_in_left, closest_in_right)
""" cross_strip contains the points, whose Xcoords are at a """
cross_strip contains the points, whose Xcoords are at a
distance(< closest_pair_dis) from mid's Xcoord distance(< closest_pair_dis) from mid's Xcoord
""" """
@ -119,6 +124,10 @@ def closest_pair_of_points_sqr(points_sorted_on_x, points_sorted_on_y, points_co
def closest_pair_of_points(points, points_counts): def closest_pair_of_points(points, points_counts):
"""
>>> closest_pair_of_points([(2, 3), (12, 30)], len([(2, 3), (12, 30)]))
28.792360097775937
"""
points_sorted_on_x = column_based_sort(points, column = 0) points_sorted_on_x = column_based_sort(points, column = 0)
points_sorted_on_y = column_based_sort(points, column = 1) points_sorted_on_y = column_based_sort(points, column = 1)
return (closest_pair_of_points_sqr(points_sorted_on_x, return (closest_pair_of_points_sqr(points_sorted_on_x,
@ -129,5 +138,3 @@ def closest_pair_of_points(points, points_counts):
if __name__ == "__main__": if __name__ == "__main__":
points = [(2, 3), (12, 30), (40, 50), (5, 1), (12, 10), (3, 4)] points = [(2, 3), (12, 30), (40, 50), (5, 1), (12, 10), (3, 4)]
print("Distance:", closest_pair_of_points(points, len(points))) print("Distance:", closest_pair_of_points(points, len(points)))