blob: bdfbad24263c76f23eb1dcdc8133aad19284541d (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
|
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[:]))
|
