def nth_permutation(n, list_):
permutation = list()
num_permutations = Basic.factorial(len(list_))
n %= num_permutations
while n > 0:
permutations_per_index = num_permutations // len(list_)
index = n // permutations_per_index
n %= permutations_per_index
num_permutations = permutations_per_index
permutation.append(list_.pop(index))
permutation += list_
return permutation
def n_choose_k(n, k):
n_fact = Basic.factorial(n)
nk_fact = Basic.factorial(n - k)
k_fact = Basic.factorial(k)
return n_fact // (k_fact * nk_fact)
def solve020(num):
factorial = Basic.factorial(num)
return General.sum_of_digits(factorial)