def cocktail_sort( arr ):
arr_len = len( arr )
half = arr_len / 2
for i in xrange( half ):
for j in xrange( i, arr_len - i - 1 ):
if arr[j] > arr[1 + j]:
arr[j], arr[1 + j] = arr[1 + j], arr[j]
for j in xrange( arr_len - i - 1, i, -1 ):
if arr[j - 1] > arr[j]:
arr[j - 1], arr[j] = arr[j], arr[j - 1]
if __name__ == "__main__":
from random import randint
arr = [ randint( 1, 110 ) for i in xrange( 100 ) ]
print arr
cocktail_sort( arr )
print arr