radix_sort.py

# 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