如何获取所有子字符串的所有子字符串和所有字符排列？ [复制]

Question

我有一个字符串 f.e. str = 'abc'

我想得到这样的所有组合：

'a', 'b', 'c', 'ab', 'ac', 'ba', 'bc', 'ca','cb', 'abc', 'acb', 'bca' , 'bac', 'cab', 'cba'

我试过了

def string_set(str):
    n = len(str) 
    arr = [] 

    for i in range(0,n):  
        for j in range(i,n): 
            arr.append(str[i:(j+1)])

    return arr

但它给了我：

'a', 'ab', 'abc', 'b', 'bc', 'c'. 

我怎样才能包括其余的？

Answer 1

import itertools

---

你可以这样做，使用 itertools permutations & combinations:

def string_set(x):
    arr = [''.join(l) for i in range(len(x)) for l in itertools.combinations(x, i+1)]     
    reslist=[]   
    for eachpermut in arr:
        for each in [''.join(eachpermut) for eachpermut in list(itertools.permutations(eachpermut))]:
            reslist.append(each)
    return reslist

如果您喜欢一行中的所有内容：

def string_set(x):
    return [each for eachpermut in [''.join(l) for i in range(len(x)) for l in itertools.combinations(x, i+1)] for each in [''.join(eachpermut) for eachpermut in list(itertools.permutations(eachpermut))]]

string_set('abc') 返回：

['a',
 'b',
 'c',
 'ab',
 'ba',
 'ac',
 'ca',
 'bc',
 'cb',
 'abc',
 'acb',
 'bac',
 'bca',
 'cab',
 'cba']

---

如果你不想导入itertools，你可以只使用他们的permutations函数：

def permutations(iterable, r=None):
    # permutations('ABCD', 2) --> AB AC AD BA BC BD CA CB CD DA DB DC
    # permutations(range(3)) --> 012 021 102 120 201 210
    pool = tuple(iterable)
    n = len(pool)
    r = n if r is None else r
    if r > n:
        return
    indices = list(range(n))
    cycles = list(range(n, n-r, -1))
    yield tuple(pool[i] for i in indices[:r])
    while n:
        for i in reversed(range(r)):
            cycles[i] -= 1
            if cycles[i] == 0:
                indices[i:] = indices[i+1:] + indices[i:i+1]
                cycles[i] = n - i
            else:
                j = cycles[i]
                indices[i], indices[-j] = indices[-j], indices[i]
                yield tuple(pool[i] for i in indices[:r])
                break
        else:
            return

然后只需在上面的代码中使用permutations 而不是itertools.permutations。

combinations 也可以这样做。