leetcode -- Letter Combinations of a Phone Number -- 重点

class Solution(object):

def dfs(self, digits, target_lvl, mydict, subres, res):
lvl = len(subres)
if lvl == target_lvl:
if subres:
res.append(subres[:])
return
else:

for x in mydict[digits[lvl]]:#子节点为下一个数字对应的每个字母
self.dfs(digits, target_lvl, mydict, subres + x, res)

def letterCombinations(self, digits):
"""
:type digits: str
:rtype: List[str]
"""
mydict = {'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 = []
self.dfs(digits, len(digits), mydict, "",res)
return res

自己重写code

class Solution(object):

def dfs(self, candidates, level, mydict, subres, res):
if level == len(candidates):
res.append(subres)
return#不要忘记return

for j in mydict[candidates[level]]:#每一个level对应一个数字
self.dfs(candidates, level + 1, mydict, subres + j, res)

def letterCombinations(self, digits):
"""
:type digits: str
:rtype: List[str]
"""
mydict = {'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']
}
if not digits: return []
res = []
self.dfs(digits, 0, mydict, '', res)
return res