mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-10-06 13:49:30 +00:00
7f04e5cd34
* spelling corrections * review * improved documentation, removed redundant variables, added testing * added type hint * camel case to snake case * spelling fix * review * python --> Python # it is a brand name, not a snake * explicit cast to int * spaces in int list * "!= None" to "is not None" * Update comb_sort.py * various spelling corrections in documentation & several variables naming conventions fix * + char in file name * import dependency - bug fix Co-authored-by: John Law <johnlaw.po@gmail.com>
74 lines
2.2 KiB
Python
74 lines
2.2 KiB
Python
"""
|
|
This is pure Python implementation of counting sort algorithm
|
|
For doctests run following command:
|
|
python -m doctest -v counting_sort.py
|
|
or
|
|
python3 -m doctest -v counting_sort.py
|
|
For manual testing run:
|
|
python counting_sort.py
|
|
"""
|
|
|
|
|
|
def counting_sort(collection):
|
|
"""Pure implementation of counting sort algorithm in Python
|
|
:param collection: some mutable ordered collection with heterogeneous
|
|
comparable items inside
|
|
:return: the same collection ordered by ascending
|
|
Examples:
|
|
>>> counting_sort([0, 5, 3, 2, 2])
|
|
[0, 2, 2, 3, 5]
|
|
>>> counting_sort([])
|
|
[]
|
|
>>> counting_sort([-2, -5, -45])
|
|
[-45, -5, -2]
|
|
"""
|
|
# if the collection is empty, returns empty
|
|
if collection == []:
|
|
return []
|
|
|
|
# get some information about the collection
|
|
coll_len = len(collection)
|
|
coll_max = max(collection)
|
|
coll_min = min(collection)
|
|
|
|
# create the counting array
|
|
counting_arr_length = coll_max + 1 - coll_min
|
|
counting_arr = [0] * counting_arr_length
|
|
|
|
# count how much a number appears in the collection
|
|
for number in collection:
|
|
counting_arr[number - coll_min] += 1
|
|
|
|
# sum each position with it's predecessors. now, counting_arr[i] tells
|
|
# us how many elements <= i has in the collection
|
|
for i in range(1, counting_arr_length):
|
|
counting_arr[i] = counting_arr[i] + counting_arr[i - 1]
|
|
|
|
# create the output collection
|
|
ordered = [0] * coll_len
|
|
|
|
# place the elements in the output, respecting the original order (stable
|
|
# sort) from end to begin, updating counting_arr
|
|
for i in reversed(range(0, coll_len)):
|
|
ordered[counting_arr[collection[i] - coll_min] - 1] = collection[i]
|
|
counting_arr[collection[i] - coll_min] -= 1
|
|
|
|
return ordered
|
|
|
|
|
|
def counting_sort_string(string):
|
|
"""
|
|
>>> counting_sort_string("thisisthestring")
|
|
'eghhiiinrsssttt'
|
|
"""
|
|
return "".join([chr(i) for i in counting_sort([ord(c) for c in string])])
|
|
|
|
|
|
if __name__ == "__main__":
|
|
# Test string sort
|
|
assert "eghhiiinrsssttt" == counting_sort_string("thisisthestring")
|
|
|
|
user_input = input("Enter numbers separated by a comma:\n").strip()
|
|
unsorted = [int(item) for item in user_input.split(",")]
|
|
print(counting_sort(unsorted))
|