在 Python 中按字典顺序生成排列

Question

I am struggling with the following, is my code correct and how to test if it works?

Task: Take a string as a single input argument. You may assume the string consists of distinct lower case letters (in alphabetical order). You may assume the input is a string of letters in alphabetical order.

Return a list of strings where each string represents a permutation of the input string. The list of permutations must be in lexicographic order. (This is basically the ordering that dictionaries use. Order by the first letter (alphabetically), if tie then use the second letter, etc.

• If the string contains a single character return a list containing that string
• Loop through all character positions of the string containing the characters to be permuted, for each character:
• Form a simpler string by removing the character
• Generate all permutations of the simpler string recursively
• Add the removed character to the front of each permutation of the simpler word, and add the resulting permutation to a list
• Return all these newly constructed permutations

[My code]

def perm_gen_lex(in_string):

    if (len(in_string) <= 1):
        return(in_string)

    # List of all new combinations
    empty_list = []

    # All permutations
    final_perm = perm_gen_lex(in_string[1:])

    # Character to be removed
    remove_char = in_string(0)

    # Remaining part of string
    remaining_string = in_string[1:]

    for perm in final_perm[1:]:
        for i in range(len(in_string) + 1):
            return empty_list.append(perm[:i] + remove_char + perm[i:])

    return empty_list

Answer 1

Some variation on this will get you moving:

from itertools import product

def combinations(string):
    return [''.join(i) for i in product(string, repeat = len(string))]

print(combinations("abc"))

See https://docs.python.org/3/library/itertools.html#itertools.product