排列列表中的重复项

Question

I am using the permutations function from the itertools library to print a list of permutations for a string. In this case, it is baca . However, the output list has duplicates of each element element. Here it is:

['aabc', 'aabc', 'aacb', 'aacb', 'abac', 'abac', 'abca', 'abca', 'acab', 'acab', 'acba', 'acba', 'baac', 'baac', 'baca', 'baca', 'bcaa', 'bcaa', 'caab', 'caab', 'caba', 'caba', 'cbaa', 'cbaa']

Here is my code. It's pretty straight forward. I don't see anything in my code that would produce this behavior.

from itertools import permutations

def rearrangeWord(word):
    p = [''.join(i) for i in permutations(word) ]
    print(sorted(p))

rearrangeWord('baca')

Answer 1

multiset_permutations can find the permutations with multiple items.

>>> from sympy.utilities.iterables import multiset_permutations
>>> s = 'baca'


>>> for item in multiset_permutations(s):
    print(item)


['a', 'a', 'b', 'c']
['a', 'a', 'c', 'b']
['a', 'b', 'a', 'c']
['a', 'b', 'c', 'a']
['a', 'c', 'a', 'b']
['a', 'c', 'b', 'a']
['b', 'a', 'a', 'c']
['b', 'a', 'c', 'a']
['b', 'c', 'a', 'a']
['c', 'a', 'a', 'b']
['c', 'a', 'b', 'a']
['c', 'b', 'a', 'a']

Answer 2

You are duplicating all 'aa' permutations.

print(sorted(set(p)))

Answer 3

If you sort the word first (which is much cheaper), you don't need to sort afterwards:

>>> [*dict.fromkeys(map(''.join, permutations(sorted('baca'))))]
['aabc', 'aacb', 'abac', 'abca', 'acab', 'acba', 'baac', 'baca', 'bcaa', 'caab', 'caba', 'cbaa']

Answer 4

This solved my problem:

print(sorted(dict.fromkeys(p)))

Now this is the output:

['aabc', 'aacb', 'abac', 'abca', 'acab', 'acba', 'baac', 'baca', 'bcaa', 'caab', 'caba', 'cbaa']