Python Program for ShellSort

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Python Program for ShellSort

In shellSort, we make the array h-sorted for a large value of h. We keep reducing the value of h until it becomes 1. An array is said to be h-sorted if all sublists of every h\’th element is sorted.

# Python program for implementation of Shell Sort
def shellSort(arr):
    # Start with a big gap, then reduce the gap
    n = len(arr)
    gap = n/2
    # Do a gapped insertion sort for this gap size.
    # The first gap elements a[] are already in gapped 
    # order keep adding one more element until the entire array
    # is gap sorted
    while gap > 0:
        for i in range(gap,n):
            # add a[i] to the elements that have been gap sorted
            # save a[i] in temp and make a hole at position i
            temp = arr[i]
            # shift earlier gap-sorted elements up until the correct
            # location for a[i] is found
            j = i
            while  j >= gap and arr[j-gap] >temp:
                arr[j] = arr[j-gap]
                j -= gap
            # put temp (the original a[i]) in its correct location
            arr[j] = temp
        gap /= 2
# Driver code to test above
arr = [ 12, 34, 54, 2, 3]
n = len(arr)
print ("Array before sorting:")
for i in range(n):
print ("\nArray after sorting:")
for i in range(n):


Array before sorting:
12 34 54 2 3 
Array after sorting:
2 3 12 34 54

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