017 letter combinations of a phone number
17. Letter Combinations of a Phone Number
题目:
https://leetcode.com/problems/letter-combinations-of-a-phone-number/
难度:
Medium
思路：
- hash table一个，用来对应digit -> letter
- s用来记录结果，每次从digits里面去一个，然后寻找其可能的char，加到s中，digits长度减小
- digits长度为0时候，把它加入结果
class Solution(object):
def letterCombinations(self, digits):
"""
:type digits: str
:rtype: List[str]
"""
if digits == '':
return []
self.res = []
self.singleResult('', digits)
return self.res
def singleResult(self, s, digits):
if len(digits) == 0:
self.res.append(s)
else:
mapx = {'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']}
cur_digit = digits[0]
for c in mapx[cur_digit]:
self.singleResult(s+c, digits[1:])
