"""
file: quickSort.py
version: python3
author: Arthur Nunes-Harwitt, Ivona Bezakova
purpose: Implementation of the quick-sort algorithm ( not in-place )
"""

def quickSort( L ):
   """
   quickSort: List( A ) -> List( A )
      where A is 'totally ordered'
   """
   if L == []:
      return []
   else:
      pivot = L[0]
      ( less, same, more ) = partition( pivot, L )
      return quickSort( less ) + same + quickSort( more )

def partition( pivot, L ):
   """
   partition: A * List( A ) -> Tuple( List( A ), List( A ), List( A ) )
      where A is totally ordered
   """
   ( less, same, more ) = ( [], [], [] )
   for e in L:
      if e < pivot:
         less.append( e )
      elif e > pivot:
         more.append( e )
      else:
         same.append( e )
   return ( less, same, more )

print( quickSort( [1, 5, 3, 4, 2, 2, 7, 5, 3, 4, 9, 0, 1, 2, 5, 4, 76, 6] ) )