LeetCode-17、电话号码的字母组合-中等

LeetCode-17、电话号码的字母组合-中等

示例:

输入："23"
输出：["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].

说明:
尽管上面的答案是按字典序排列的，但是你可以任意选择答案输出的顺序。

 

代码：列表推导

class Solution:
    def letterCombinations(self, digits: str) -> List[str]:
        dic = {}
        ind = 97
        for i in range(2, 10):
            if i == 7 or i == 9:
                dic[str(i)] = chr(ind) + chr(ind+1) + chr(ind+2) + chr(ind+3)
                ind = ind + 4
            else:
                dic[str(i)] = chr(ind) + chr(ind+1) + chr(ind+2)
                ind = ind + 3

        if digits == '':
            return []
        res = ['']
        for num in digits:
            res = [pre + nex for pre in res for nex in dic[num]]
        return res