限制排列

Question

I want to permute each a set of elements.. However, for each element in the set. I want to limit the times its going to be repeated.

Here is a snip of code to understand:

_list_ = [0,1,3]

limit_dict = {
    
    0 : [0, 1],
    1 : [0, 3],
    3 : [0, 1]

}

def main(position=0, length=5, genlist=[]):

    if position == length:
        print (genlist)

    else:

        for element in _list_:

            if limit_dict[element][0] != limit_dict[element][1]:

                limit_dict[element][0] += 1

                main(position + 1, length, genlist + [element])

                limit_dict[element][0] -= 1

main()

This is the general idea, is there a faster way to implement this?

I want to do something like this for a large number of integers and therefore cannot use itertools to achieve this since it uses a lot of memory.

Answer 1

That's what distinct_permutations from more-itertools does.

from more_itertools import distinct_permutations

limit_dict = {
    0 : [0, 1],
    1 : [0, 3],
    3 : [0, 1]
}

elements = (k for k, v in limit_dict.items() for _ in range(*v))
for permutation in distinct_permutations(elements):
    print(permutation)

Output:

(0, 1, 1, 1, 3)
(0, 1, 1, 3, 1)
(0, 1, 3, 1, 1)
(0, 3, 1, 1, 1)
(1, 0, 1, 1, 3)
(1, 0, 1, 3, 1)
(1, 0, 3, 1, 1)
(1, 1, 0, 1, 3)
(1, 1, 0, 3, 1)
(1, 1, 1, 0, 3)
(1, 1, 1, 3, 0)
(1, 1, 3, 0, 1)
(1, 1, 3, 1, 0)
(1, 3, 0, 1, 1)
(1, 3, 1, 0, 1)
(1, 3, 1, 1, 0)
(3, 0, 1, 1, 1)
(3, 1, 0, 1, 1)
(3, 1, 1, 0, 1)
(3, 1, 1, 1, 0)