求字符串的组合

求字符串的组合

"""
求字符串的组合
"""


def combination_k(s, k):
    if k == 0:
        return ['']
    subletters = []
    for i in range(len(s)):
        for letter in combination_k(s[i + 1:], k - 1):
            subletters += [s[i] + letter]
    return subletters


def combine(s):
    length = len(s)
    res = []
    while length:
        res += combination_k(s, length)
        length -= 1
    return res

if __name__ == '__main__':
    res = combine('abc')
    print(res)