Python Program for Radix Sort

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In this article we are going to see Radix Sort with Python

Radix Sort Algorithm Python

The provided Python code implements Radix Sort, a non-comparative sorting algorithm that works by distributing elements into buckets based on their individual digits. The code defines a countingSort function, which performs counting sort based on the digit represented by exp1. It maintains auxiliary arrays count and output to store intermediate results. The radixSort function orchestrates the sorting process by repeatedly applying counting sort for each digit position, from the least significant digit to the most significant digit. The driver code initializes an array, applies the radixSort function, and prints the sorted array. This algorithm’s time complexity is linear, making it suitable for large datasets with a limited range of digits.

Python3

# Python program for implementation of Radix Sort 
   
# A function to do counting sort of arr[] according to 
# the digit represented by exp. 
def countingSort(arr, exp1): 
   
    n = len(arr) 
   
    # The output array elements that will have sorted arr 
    output = [0] * (n) 
   
    # initialize count array as 0 
    count = [0] * (10) 
   
    # Store count of occurrences in count[] 
    for i in range(0, n): 
        index = (arr[i]/exp1) 
        count[int((index)%10)] += 1
   
    # Change count[i] so that count[i] now contains actual 
    #  position of this digit in output array 
    for i in range(1,10): 
        count[i] += count[i-1] 
   
    # Build the output array 
    i = n-1
    while i>=0: 
        index = (arr[i]/exp1) 
        output[ count[ int((index)%10) ] - 1] = arr[i] 
        count[int((index)%10)] -= 1
        i -= 1
   
    # Copying the output array to arr[], 
    # so that arr now contains sorted numbers 
    i = 0
    for i in range(0,len(arr)): 
        arr[i] = output[i] 
 
# Method to do Radix Sort
def radixSort(arr):
 
    # Find the maximum number to know number of digits
    max1 = max(arr)
 
    # Do counting sort for every digit. Note that instead
    # of passing digit number, exp is passed. exp is 10^i
    # where i is current digit number
    exp = 1
    while max1 // exp > 0:
        countingSort(arr,exp)
        exp *= 10
 
# Driver code to test above
arr = [ 170, 45, 75, 90, 802, 24, 2, 66]
radixSort(arr)
 
for i in range(len(arr)):
    print(arr[i],end=" ")
 
# This code is contributed by Mohit Kumra
# This code is updated by Sudeep Saxena(saxenasudeepcse@gmail.com) on July 9, 2020

Output

2 24 45 66 75 90 170 802

Time Complexity: O(n*d). Here d=10
Auxiliary Space: O(n)

Please refer complete article on Radix Sort for more details!

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Last Updated : 28 Aug, 2023