CODE EXAMPLE FOR PYTHON

sorted string dict approach

from collections import defaultdict


class PermutationsAlt(object):

    def is_permutation(self, str1, str2):
        if str1 is None or str2 is None:
            return False
        if len(str1) != len(str2):
            return False
        unique_counts1 = defaultdict(int)
        unique_counts2 = defaultdict(int)
        for char in str1:
            unique_counts1[char] += 1
        for char in str2:
            unique_counts2[char] += 1
        return unique_counts1 == unique_counts2