17.letter-combinations-of-a-phone-number.py

#
# @lc app=leetcode id=17 lang=python3
#
# [17] Letter Combinations of a Phone Number
#

# @lc code=start
class Solution:
    def letterCombinations(self, digits: str) -> List[str]:
        if not digits:
            return []

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

        combs = [""]
        for d in digits:
            combs = [x+y for x in combs for y in ntol_mapping[d]]
        return combs
# @lc code=end