# Write a Python Program for ShellSort 
 # 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[0..gap-1] 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(arr[i]),
  
shellSort(arr)
  
print ("\nArray after sorting:")
for i in range(n):
    print(arr[i]),
  
# This code is contributed by Mohit Kumra