019f8fd211
git-subtree-dir: users/wpcarro git-subtree-mainline:464bbcb15cgit-subtree-split:24f5a642afChange-Id: I6105b3762b79126b3488359c95978cadb3efa789
34 lines
718 B
Python
34 lines
718 B
Python
import random
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def get_random(floor, ceiling):
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return random.randrange(floor, ceiling + 1)
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# shuffle_in_place :: [a] -> IO ()
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def shuffle_in_place(xs):
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"""Fisher-Yates algorithm. Notice that shuffling here is the same as
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selecting a random permutation of the input set, `xs`."""
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n = len(xs) - 1
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for i in range(len(xs)):
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r = get_random(i, n)
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xs[i], xs[r] = xs[r], xs[i]
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return xs
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# shuffle :: [a] -> [a]
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def shuffle_not_in_place(xs):
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result = []
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while xs:
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i = get_random(0, len(xs) - 1)
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x = xs.pop(i)
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result.append(x)
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return result
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xs = [x for x in range(9)]
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print(xs)
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# print(shuffle_not_in_place(xs))
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print(shuffle_in_place(xs[:]))
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