#!/bin/python

"""
Write a recursive function for generating all permutations of an input string. Return them as a set.
"""

def get_permutations(string):

    if len(string) < 2:
        return set([string])

    all_chars_except_last = string[:-1]
    last_char = string[-1]

    permutations_of_all_chars_except_last = get_permutations(all_chars_except_last)

    permutations = set()
    for permutation_of_all_chars_except_last in permutations_of_all_chars_except_last:
        for position in range(len(all_chars_except_last) + 1):
            permutation = (
                permutation_of_all_chars_except_last[:position]
                + last_char
                + permutation_of_all_chars_except_last[position:]
            )
            permutations.add(permutation)

    
    return permutations


str = "abcd"
print get_permutations(str)