17. Letter Combinations of a Phone Number (Medium) - TengnanYao/daily_leetcode GitHub Wiki

class Solution(object):
    def letterCombinations(self, digits):
        """
        :type digits: str
        :rtype: List[str]
        """
        h = {
            "2": "abc",
            "3": "def",
            "4": "ghi",
            "5": "jkl",
            "6": "mno",
            "7": "pqrs",
            "8": "tuv",
            "9": "wxyz"
        }
        result = []
        for d in digits:
            if not result:
                result = list(h[d])
            else:
                result = [r + c for r in result for c in h[d]]
        return result