打卡群刷题总结0824——电话号码的字母组合

class Solution(object):
    def dfs(self, digits, cur):
        if len(digits) == 0:
            self.res.append(cur)
        else:
            for s in self.d[digits[0]]:
                cur2 = cur + s
                self.dfs(digits[1:], cur2)
    
    def letterCombinations(self, digits):
        """
        :type digits: str
        :rtype: List[str]
        """
        if len(digits) == 0:
            return []
        number = list(map(str, range(2, 10)))
        alpha = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz']
        self.d = dict(zip(number, alpha))
        self.res = []
        self.dfs(digits, '')
        return self.res