The latest article from InterviewCake is about a very neat & elegant algorithm: Fisher-Yates shuffle algorithm
Q: how to shuffle an array - in-place?
This algorithm is really simple to understand and works very well - you don't need too much words to learn, just the code (from InterviewCake):
import random def get_random(floor, ceiling): return random.randrange(floor, ceiling + 1) def shuffle(the_list): # if it's 1 or 0 items, just return if len(the_list) <= 1: return the_list last_index_in_the_list = len(the_list) - 1 # walk through from beginning to end for index_we_are_choosing_for in xrange(0, len(the_list) - 1): # choose a random not-yet-placed item to place there # (could also be the item currently in that spot) # must be an item AFTER the current item, because the stuff # before has all already been placed random_choice_index = get_random(index_we_are_choosing_for, last_index_in_the_list) # place our random choice in the spot by swapping if random_choice_index != index_we_are_choosing_for: the_list[index_we_are_choosing_for], the_list[random_choice_index] = \ the_list[random_choice_index], the_list[index_we_are_choosing_for]
