題目描述
給定一個僅包含數字 2-9 的字符串,返回所有它能表示的字母組合。
給出數字到字母的映射如下(與電話按鍵相同)。注意 1 不對應任何字母。
思路
代碼
class Solution:
def letterCombination(self,digits):
output = []
phone = {'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'],
}
def backtrack(combination,next_digits):
if len(next_digits) == 0:
output.append(combination)
else:
for letter in phone[next_digits[0]]:
backtrack(combination+letter,next_digits[1:])
if digits:
backtrack("",digits)
return output