1 class Solution:
 2     def convertToAlpha(self,num):
 3         return chr(num+96)
 4     
 5     def freqAlphabets(self, s: str) -> str:
 6         n = len(s)
 7         q = []
 8         i = n - 1
 9         while i >= 0:
10             cur = s[i]
11             if cur == '#':
12                 num = int(s[i-2:i])
13                 q.insert(0,self.convertToAlpha(num))
14                 i -= 3
15             else:
16                 num = int(s[i])
17                 q.insert(0,self.convertToAlpha(num))
18                 i -= 1
19         return ''.join(q)

倒序遍历，遇到#则读取前2位，并转换位字母，否则读取当前位转换位字母。