Reverse Vowels in a String

StringTwo Pointers

Write a function that takes a string as input and reverses only the vowels present in it. The function should return the modified string with all non-vowel characters remaining static in their original positions. Vowels are defined as 'a', 'e', 'i', 'o', and 'u', and can appear in both lowercase and uppercase.

Example 1

Input

[
  "hello"
]

Output

holle

Explanation. The vowels 'e' and 'o' have been reversed, while the other characters remain in their original positions.

Example 2

Input

[
  "leetcode"
]

Output

leotcede

Explanation. The vowels 'e', 'e', 'o', 'e' are reversed to 'o', 'e', 'e', 'e', keeping non-vowel characters fixed.

Example 3

Input

[
  "xyz"
]

Output

xyz

Explanation. There are no vowels in the input string, so it remains unchanged.

Example 4

Input

[
  "AEIOU"
]

Output

UOIEA

Explanation. All characters are vowels and they are completely reversed.

Example 5

Input

[
  ""
]

Output

Explanation. Empty string input returns an empty string output.

Follow-up: Can you optimize your solution to use constant space?

Constraints:

The input string will not be null. The string can be empty or contain only non-vowel characters.

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