题目描述给定一个只包含数字2-9的字符串，返回它能代表的所有字母组合。可以按任何顺序返回答案。数字到字母的映射如下（与电话键相同）。请注意，1不对应任何字母。示例1：输入：digits="23"输出：["ad","ae","af","bd","be","bf","cd","ce","cf"]示例2：输入：digits=""输出：[]示例3：输入：digits="2"输出：["a","b","c"]提示：0<=digits.length<=4digits[i]是['2','9']范围内的数字。参考代码类解决方案：defletterCombinations(self,digits:str)->List[str]:ifnotdigits:return[]num_map={"2":"abc","3":"def","4":"ghi","5":"jkl","6":"mno","7":"pqrs","8":"tuv","9":"wxyz",}defdfs(idx,temp):ifidx==len(digits):ret.append(temp)else:digit=digits[idx]forcinnum_map[digit]:temp+=cdfs(idx+1,temp)#删除calculatednumbertemp=temp[:-1]temp=""ret=[]dfs(0,temp)returnret以上就是本次分享的全部内容。现在欢迎想要学习编程的小伙伴们关注Python技术大本营，获取更多技能和教程。
