tvl-depot/scratch/data_structures_and_algorithms/shuffle.py
William Carroll fabf1c9334 Tidy up structure of briefcase
I had a spare fifteen minutes and decided that I should tidy up my
monorepo. The work of tidying up is not finished; this is a small step in the
right direction.

TL;DR
- Created a tools directory
- Created a scratch directory (see README.md for more information)
- Added README.md to third_party
- Renamed delete_dotfile_symlinks -> symlinkManager
- Packaged symlinkManager as an executable symlink-mgr using buildGo
2020-02-12 16:58:29 +00:00

34 lines
718 B
Python

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[:]))