1 """
2 Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent.
3 A mapping of digit to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.
4 Example:
5 Input: "23"
6 Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
7 """
8 """
9 本题三次循环，看不懂debug一遍就好了
10 """
11 class Solution1:
12 def letterCombinations(self, digits):
13 phone = {'2': 'abc', '3': 'def', '4': 'ghi', '5': 'jkl', '6': 'mno', '7': 'pqrs', '8': 'tuv', '9': 'wxyz'}
14 digits = 23
15 if digits == '':
16 return []
17 result = ['']
18 for digit in digits:
19 lst = phone[digit]
20 newresult = []
21 for x in result: #!!!保存现有的排列组合
22 for y in lst: #
23 newresult.append(x + y)
24 result = newresult
25 return result
26
27 # phone = {'2': 'abc', '3': 'def', '4': 'ghi', '5': 'jkl', '6': 'mno', '7': 'pqrs', '8': 'tuv', '9': 'wxyz'}
28 # digits = '23'
29 # result = ['']
30 # for digit in digits:
31 # lst = phone[digit]
32 # newresult = []
33 # for x in result: #!!!保存现有的排列组合
34 # for y in lst: #
35 # newresult.append(x + y)
36 # result = newresult
37 #
38 # print(result)
