"""
Illustrate how to implement bucket sort algorithm.
Author: OMKAR PATHAK
This program will illustrate how to implement bucket sort algorithm
Wikipedia says: Bucket sort, or bin sort, is a sorting algorithm that works
by distributing the elements of an array into a number of buckets.
Each bucket is then sorted individually, either using a different sorting
algorithm, or by recursively applying the bucket sorting algorithm. It is a
distribution sort, and is a cousin of radix sort in the most to least
significant digit flavour.
Bucket sort is a generalization of pigeonhole sort. Bucket sort can be
implemented with comparisons and therefore can also be considered a
comparison sort algorithm. The computational complexity estimates involve the
number of buckets.
Time Complexity of Solution:
Worst case scenario occurs when all the elements are placed in a single bucket.
The overall performance would then be dominated by the algorithm used to sort each
bucket. In this case, O(n log n), because of TimSort
Average Case O(n + (n^2)/k + k), where k is the number of buckets
If k = O(n), time complexity is O(n)
Source: https://en.wikipedia.org/wiki/Bucket_sort
"""
from __future__ import annotations
def bucket_sort(my_list: list, bucket_count: int = 10) -> list:
"""
>>> data = [-1, 2, -5, 0]
>>> bucket_sort(data) == sorted(data)
True
>>> data = [9, 8, 7, 6, -12]
>>> bucket_sort(data) == sorted(data)
True
>>> data = [.4, 1.2, .1, .2, -.9]
>>> bucket_sort(data) == sorted(data)
True
>>> bucket_sort([]) == sorted([])
True
>>> data = [-1e10, 1e10]
>>> bucket_sort(data) == sorted(data)
True
>>> import random
>>> collection = random.sample(range(-50, 50), 50)
>>> bucket_sort(collection) == sorted(collection)
True
"""
if len(my_list) == 0 or bucket_count <= 0:
return []
min_value, max_value = min(my_list), max(my_list)
bucket_size = (max_value - min_value) / bucket_count
buckets: list[list] = [[] for _ in range(bucket_count)]
for val in my_list:
index = min(int((val - min_value) / bucket_size), bucket_count - 1)
buckets[index].append(val)
return [val for bucket in buckets for val in sorted(bucket)]
if __name__ == "__main__":
from doctest import testmod
testmod()
assert bucket_sort([4, 5, 3, 2, 1]) == [1, 2, 3, 4, 5]
assert bucket_sort([0, 1, -10, 15, 2, -2]) == [-10, -2, 0, 1, 2, 15]