tvl-depot/users/wpcarro/scratch/data_structures_and_algorithms/shuffle.py

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import random
def get_random(floor, ceiling):
return random.randrange(floor, ceiling + 1)
# shuffle_in_place :: [a] -> IO ()
def shuffle_in_place(xs):
"""Fisher-Yates algorithm. Notice that shuffling here is the same as
selecting a random permutation of the input set, `xs`."""
n = len(xs) - 1
for i in range(len(xs)):
r = get_random(i, n)
xs[i], xs[r] = xs[r], xs[i]
return xs
# shuffle :: [a] -> [a]
def shuffle_not_in_place(xs):
result = []
while xs:
i = get_random(0, len(xs) - 1)
x = xs.pop(i)
result.append(x)
return result
xs = [x for x in range(9)]
print(xs)
# print(shuffle_not_in_place(xs))
print(shuffle_in_place(xs[:]))