Python Program for Counting Sort Using counter method.

Python Program for Counting Sort Using sorted() and reduce():

This program implements the Counting Sort algorithm using the collections.Counter() method in Python. Counting Sort is a sorting algorithm that works by counting the occurrence of each distinct element in the input list and using that information to determine the position of each element in the output list. The algorithm has a time complexity of O(n+k), where n is the number of elements in the input list and k is the range of the input data, and a space complexity of O(k).

Algorithm:

1.Convert the input string into a list of characters.
2.Count the occurrence of each character in the list using the collections.Counter() method.
3.Sort the keys of the resulting Counter object to get the unique characters in the list in sorted order.
4.For each character in the sorted list of keys, create a list of repeated characters using the corresponding count from the Counter object.
5.Concatenate the lists of repeated characters to form the sorted output list.

Python3

from collections import Counter
 
def counting_sort(arr):
    count = Counter(arr)
    output = []
    for c in sorted(count.keys()):
        output +=  * count
    return output
 
arr = "w3wiki"
arr = list(arr)
arr = counting_sort(arr)
output = ''.join(arr)
print("Sorted character array is", output)

Output

Sorted character array is eeeefggkkorss

Time Complexity: O(nlogn) due to the use of the sorted() method, but O(n+k) in the best case when k is small.

Space Complexity: O(k) for the count array and output list.