Given a string containing digits from 2-9
inclusive, return all possible letter combinations that the number could represent.
A mapping of digit to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.
Example:
Input: "23" Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.
LeetCode:链接
穷举所有可能的字符串使用dfs来解决。
class Solution(object):
def letterCombinations(self, digits):
"""
:type digits: str
:rtype: List[str]
"""
def dfs(num, string, res):
if num == len(digits):
res.append(string)
return
for letter in dict[digits[num]]:
dfs(num+1, string+letter, res)
if not digits:
return []
dict={'2':['a','b','c'],
'3':['d','e','f'],
'4':['g','h','i'],
'5':['j','k','l'],
'6':['m','n','o'],
'7':['p','q','r','s'],
'8':['t','u','v'],
'9':['w','x','y','z']}
res = []
dfs(0, "", res)
return res