Leetcode 17. 电话号码的字母组合(Python3)

17. 电话号码的字母组合

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。

示例:

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

代码：

class Solution(object):
    def letterCombinations(self, digits):
        if len(digits) == 0:
            return []
        dic = {'2':'abc','3':'def','4':'ghi','5':'jkl','6':'mno','7':'pqrs','8':'tuv','9':'wxyz'}
        strs = [dic[i] for i in digits]
        stack = [ch for ch in strs[0]]
        for i in range(1,len(strs)):
            iters = len(stack)
            for _ in range(iters):
                temp = stack.pop(0)
                for ch in strs[i]:
                    stack.append(temp+ch)
        return stack