Source code for toqito.perms.unique_perms

"""Calculate unique permutations."""
from dataclasses import dataclass


@dataclass
class UniqueElement:
    """Class for unique elements to keep track of occurrences."""

    value: int
    occurrences: int


[docs]def unique_perms(elements: list[int]): r""" Determine the number of unique permutations of a list. Examples ========== Consider the following vector .. math:: \left[1, 1, 2, 2, 1, 2, 1, 3, 3, 3\right]. The number of possible permutations possible with the above vector is :math:`4200`. This can be obtained using the :code:`toqito` package as follows. >>> from toqito.perms import unique_perms >>> vec_nums = [1, 1, 2, 2, 1, 2, 1, 3, 3, 3] >>> len(list(unique_perms(vec_nums))) 4200 :param elements: List of integers. :return: The number of possible permutations possible. """ elem_set = set(elements) list_unique = [UniqueElement(value=i, occurrences=elements.count(i)) for i in elem_set] len_elems = len(elements) return perm_unique_helper(list_unique, [0] * len_elems, len_elems - 1)
def perm_unique_helper(list_unique: list[UniqueElement], result_list: list[int], elem_d: int): """ Provide helper function for unique_perms. :param list_unique: :param result_list: :param elem_d: :return: """ if elem_d < 0: yield tuple(result_list) else: for i in list_unique: if i.occurrences > 0: result_list[elem_d] = i.value i.occurrences -= 1 for g_perm in perm_unique_helper(list_unique, result_list, elem_d - 1): yield g_perm i.occurrences += 1