leetcode 深度搜尋 1641.統計字典序母音字串的數目

class Solution:
    def countVowelStrings(self, n: int) -> int:
        result = 0
        s="aeiou"
        def dfs(s,res):
            nonlocal result
            if len(res)==n:
                result+=1
                return
            if len(s)==0:
                return 
            for i in range(len(s)): 
                dfs(s[i:],res+s[i])
        dfs(s,"") 
        return result