在Python中for循環中的遞歸可視化

Question

我在為以下排列代碼繪制遞歸樹時遇到麻煩：

def permut(array):

    if len(array) == 1:
        return [array]
    res = []
    for permutation in permut(array[1:]):
        print permutation, array
        for i in range(len(array)):
            res.append(permutation[:i] + array[0:1] + permutation[i:])
    return res

假設我的數組是'mick'，然后得到以下打印輸出以用於排列和數組：

k和ck

ck and ick

kc和ick

ick and mick

我理解它直到'k'和'ck'（就像array ='ck'len（arraw [1：]）== 1）一樣，但是我們如何在遞歸中得到'ick'作為數組呢？ 你能想像一下嗎？ 非常感謝您提供的任何提示！

Answer 1

permut('Mick')                 # recursion: for permutation in permut('ick')
    permut('ick')              # recursion: for permutation in permut('ck')
        permut('ck')           # recursion: for permutation in permut('k')
            permut('k')        # return ['k']
        permut('ck')           # continue from the loop
                               # print each element of ['k'] with 'ck'
                               # return res, which is ['ck', 'kc']
    permut('ick')              # continue from the loop
                               # print each of ['ck', 'kc'] with 'ick'
                               # return res, which is ['ick', 'cik', 'cki', 'ikc', 'kic', 'kci']
permut('Mick')                 # continue from loop
                               # print each of the above elements + 'Mick' individually
                               # return res, which is... long

以上基本上排列了單詞中的所有字母，這可以簡單地通過

>>> import itertools as it
>>> res = list(''.join(p) for p in it.permutations('Mick'))
>>> print res
['Mick', 'Mikc', 'Mcik', 'Mcki', 'Mkic', 'Mkci', 'iMck', 'iMkc', 'icMk', 'ickM', 'ikMc', 'ikcM', 'cMik', 'cMki', 'ciMk', 'cikM', 'ckMi', 'ckiM', 'kMic', 'kMci', 'kiMc', 'kicM', 'kcMi', 'kciM']