Reverse vowels of a string

Time: O(N); Space: O(1); easy

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

Example 1:

Input: s = “hello”

Output: “holle”

Example 2:

Input: s = “leetcode”

Output: “leotcede”

Note:

  • The vowels does not include the letter “y”.

[1]:

class Solution1(object):
    """
    Time: O(N)
    Space: O(1)
    """
    def reverseVowels(self, s):
        """
        :type s: str
        :rtype: str
        """
        vowels = "aeiou"
        string = list(s)
        i, j = 0, len(s) - 1
        while i < j:
            if string[i].lower() not in vowels:
                i += 1
            elif string[j].lower() not in vowels:
                j -= 1
            else:
                string[i], string[j] = string[j], string[i]
                i += 1
                j -= 1
        return ''.join(string)

[3]:

sol = Solution1()

s = "hello"
assert sol.reverseVowels(s) == "holle"

s = "leetcode"
assert sol.reverseVowels(s) == "leotcede"