Letter combinations from numbers

letter_combinations_from_numbers.py

"""
https://scammingthecodinginterview.com
Week 4: Strings
Problem: 1
"""


class Solution(object):

    def solve(self, numbers):

        mapping = {
            '2': 'abc', '3': 'def', '4': 'ghi', '5': 'jkl',
            '6': 'mno', '7': 'pqrs', '8': 'tuv', '9': 'wxyz'
        }

        if len(numbers) == 0:
            return []
        if len(numbers) == 1:
            return list(mapping[numbers[0]])

        previous_combinations = self.solve(numbers[:-1])
        current_numbers = mapping[numbers[-1]]

        complete_conbinations = [
            comb + s for s in current_numbers for comb in previous_combinations
        ]

        return complete_conbinations


if __name__ == "__main__":

    a = "23"
    ans = Solution().solve(a)

    print(sorted(ans))