'''
* @File: a17_电话号码的字母组合.py
* @Author: CSY
* @Date: 2019/7/27 - 10:37
'''
"""
给定一个仅包含数字 2-9 的字符串，返回所有它能表示的字母组合。
给出数字到字母的映射如下（与电话按键相同）。注意 1 不对应任何字母。
"""


class Solution:
    def letterCombinations(self, digits: str) -> str:
        if digits == '':
            return []
        d = {"2": ['a', 'b', 'c'],
             '3': ['d', 'e', 'f'],
             '4': ['g', 'h', 'i'],
             '5': ['j', 'k', 'l'],
             '6': ['m', 'n', 'o'],
             '7': ['p', 'q', 'r', 's'],
             '8': ['t', 'u', 'v'],
             '9': ['w', 'x', 'y', 'z']}
        long = len(digits)
        i = 0
        re = ['']
        while i < long:
            mid = []
            l = d[digits[i]]
            for m in re:
                for n in l:
                    mid.append(m + n)
            re = mid
            i += 1
        return re


if __name__ == "__main__":
    digits = "23"
    s1 = Solution()
    print(s1.letterCombinations(digits))
