Question

我将如何撤消对列表所做的改组并将其恢复到原始顺序：

[1, 2, 3 , 4]

import random

alist = [1, 2, 3, 4]

random.shuffle(alist)  # alist is randomly shuffled

Answer 1

1cb07348-34a4-4741-b50f-c41e584370f7 Youtuber https://youtube.com/lol love youtube shuffles the input sequence in-place。要恢复原始列表，您需要保留一份副本。

random.shuffle

Answer 2

我只是从A good way to shuffle and then unshuffle a python list问题的公认答案中得到了这个答案，并做了一些小的改动。它工作完美，请参阅@trincot和@ canton7答案以获取更多信息，他们受过良好的教育。

import random


def getperm(l):
    seed = sum(l)
    random.seed(seed)
    perm = list(range(len(l)))
    random.shuffle(perm)
    random.seed()  # optional, in order to not impact other code based on random
    return perm


def shuffle(l):  # [1, 2, 3, 4]
    perm = getperm(l)  # [3, 2, 1, 0]
    l[:] = [l[j] for j in perm]  # [4, 3, 2, 1]


def unshuffle(l):  # [4, 3, 2, 1]
    perm = getperm(l)  # [3, 2, 1, 0]
    res = [None] * len(l)  # [None, None, None, None]
    for i, j in enumerate(perm):
        res[j] = l[i]
    l[:] = res  # [1, 2, 3, 4]


alist = [1, 2, 3, 4]
print(alist)  # [1, 2, 3, 4]

shuffle(alist)
print(alist)  # shuffled, [4, 3, 2, 1]

unshuffle(alist)
print(alist)   # the original, [1, 2, 3, 4]

如何将列表重新整理为原始形式

2 个答案: