Topological Sorting in Python

Python Program for Counting Sort

Last Updated : 28 Jul, 2022

Counting sort is a sorting technique based on keys between a specific range. It works by counting the number of objects having distinct key values (kind of hashing). Then doing some arithmetic to calculate the position of each object in the output sequence.

Python3

# Python program for counting sort
 
# The main function that sort the given string arr[] in 
# alphabetical order
def countSort(arr):
 
    # The output character array that will have sorted arr
    output = [0 for i in range(256)]
 
    # Create a count array to store count of individual
    # characters and initialize count array as 0
    count = [0 for i in range(256)]
 
    # For storing the resulting answer since the 
    # string is immutable
    ans = ["" for _ in arr]
 
    # Store count of each character
    for i in arr:
        count[ord(i)] += 1
 
    # Change count[i] so that count[i] now contains actual
    # position of this character in output array
    for i in range(256):
        count[i] += count[i-1]
 
    # Build the output character array
    for i in range(len(arr)):
        output[count[ord(arr[i])]-1] = arr[i]
        count[ord(arr[i])] -= 1
 
    # Copy the output array to arr, so that arr now
    # contains sorted characters
    for i in range(len(arr)):
        ans[i] = output[i]
    return ans 
 
# Driver program to test above function
arr = "geeksforgeeks"
ans = countSort(arr)
print ("Sorted character array is %s"  %("".join(ans)))
 
# This code is contributed by Nikhil Kumar Singh

Output:

Sorted character array is eeeefggkkorss

Time Complexity: O(n+k) where n is the number of elements in the input array and k is the range of input.
Auxiliary Space: O(n+k)

Please refer complete article on Counting Sort for more details!

Topological Sorting in Python

kartik

Improve

Article Tags :

Python Programs

Similar Reads

Python Program for Cocktail Sort

Cocktail Sort is a variation of Bubble sort. The Bubble sort algorithm always traverses elements from left and moves the largest element to its correct position in first iteration and second largest in second iteration and so on. Cocktail Sort traverses through a given array in both directions alter

Python Program for Comb Sort

Comb Sort is an improvement over Bubble Sort, and it aims to eliminate the problem of small values near the end of the list, which causes Bubble Sort to take more time than necessary. Comb Sort uses a larger gap for comparison, which gradually reduces until it becomes 1 (like the gap in Shell Sort).

Python Program for Bubble Sort

Bubble Sort is the simplest sorting algorithm that works by repeatedly swapping the adjacent elements if they are in the wrong order. Bubble Sort algorithm, sorts an array by repeatedly comparing adjacent elements and swapping them if they are in the wrong order. The algorithm iterates through the a

Python List Counting Programs

Python provides various methods, such as count(), dictionary-based counting, and list comprehensions, to efficiently handle counting operations. This collection of Python programs covers different ways to count elements in lists, including counting occurrences, matching elements, frequency analysis,

Python Program for ShellSort

Shell Sort is an advanced version of the insertion sort algorithm that improves its efficiency by comparing and sorting elements that are far apart. The idea behind Shell Sort is to break the original list into smaller sublists, sort these sublists, and gradually reduce the gap between the sublist e

Python Program for Insertion Sort

Insertion sort is a simple sorting algorithm that works by iteratively inserting each element of an unsorted list into its correct position in a sorted portion of the list. The insertionSort function takes an array arr as input. It first calculates the length of the array (n). If the length is 0 or

Python Program for Radix Sort

Radix Sort is a linear sorting algorithm that sorts elements by processing them digit by digit. It is an efficient sorting algorithm for integers or strings with fixed-size keys. Rather than comparing elements directly, Radix Sort distributes the elements into buckets based on each digitâ€™s value. By

Python Program for Gnome Sort

In this article we are going to see Gnome Sort with Python. Algorithm Steps: If you are at the start of the array then go to the right element (from arr[0] to arr[1]).If the current array element is larger or equal to the previous array element then go one step right if (arr[i] >= arr[i-1]) i++;I

Python Program for Pigeonhole Sort

Pigeonhole Sort is a sorting algorithm that is suitable for sorting lists of elements where the number of elements and the number of possible key values are approximately the same. It requires O(n + Range) time where n is number of elements in input array and 'Range' is number of possible values in

Python - Sort by Factor count

Given element list, sort by factor count of each element. Input : test_list = [12, 100, 22] Output : [22, 12, 100] Explanation : 3, 5, 8 factors respectively of elements. Input : test_list = [6, 11] Output : [11, 6] Explanation : 1, 4 factors respectively of elements. Method #1 : Using sort() + len(