Python Program for Radix Sort

The Radix Sort Algorithm
1) Do following for each digit i where i varies from least significant digit to the most significant digit.
………….a) Sort input array using counting sort (or any stable sort) according to the i\’th digit.

Python

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# 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[ (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[ (index)%10 ] - 1] = arr[i]
        count[ (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]),
  
# This code is contributed by Mohit Kumra

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