leetcode 345 涉及到enumerate用法

Write a function that takes a string as input and reverse only the vowels of a string.

Example 1:

Input: "hello"
Output: "holle"

Example 2:

Input: "leetcode"
Output: "leotcede"

Note:
The vowels does not include the letter "y".

代码：

class Solution:  
    def reverseVowels(self, s):  
        """ 
        :type s: str 
        :rtype: str 
        """  
        check = "aeiouAEIOU"  
        s_list = list(s)  
        keep = []  
  
        for key, value in enumerate(s_list):  
            if value in check:  
                s_list[key] = None 
                keep.append(value)  
        keep.reverse()  
  
        for key, value in enumerate(s_list):  
            if value == None:  
                if (keep):  
                    s_list[key] = keep.pop(0)  
  
        return "".join(s_list)  

1.可以看到使用enumerate使得在索引编号时更加方便

2..'join()可以使列表变成字符串