Bucket sort (Python)

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Bucket sort is possibly the simplest distribution sorting algorithm. The essential requirement is that the size of the array from which the elements to be sorted are drawn is a small, fixed constant, say n.

<<sort function>>=
def bucketSort(arr):
    initialize counters
    count amount of each array-number
    rearrange order of array
    return arr

For example, suppose that we are sorting elements drawn from {0, 1, . . ., n-1}. The integers in this set can be of the range 0 until (n-1). Bucket sort uses n counters. These counters first have to be initialized:

<<initialize counters>>=
count = [0] * len(arr)

To we can determine the amount of each number in the array we want to sort.

<<count amount of each array-number>>=
for value in arr:
    count[value] += 1

After we've determined all needed information about the array we want to sort. The array can be sorted.

<<rearrange order of array>>=
arr = []
for nr, amount in enumerate(count):
    arr.extend([nr] * amount)

Putting it together

To check the bucket sort, we output the data:

<<output the array>>=
for val in arr:
    print val,
print

Putting it all together with a example array.

<<bucketsort.py>>=
sort function
arr = [1,3,4,6,4,2,9,1,2,9]
output the array
arr = bucketSort(arr)
output the array

This generates following output:

1 3 4 6 4 2 9 1 2 9 
1 1 2 2 3 4 4 6 9 9