Reverse Vowels in a String

[
  "hello"
]

Explanation. The vowels are 'e' and 'o'. Reversing their positions while keeping 'h', 'l', 'l' in place results in 'holle'.

[
  "Leetcode"
]

Explanation. The vowels are 'e', 'e', 'o', 'e'. In order, they become 'e', 'o', 'e', 'e' when reversed relative to their original positions.

[
  "rhythm"
]

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

[
  "aeiou"
]

Explanation. All characters are vowels. Reversing them reverses the entire string.

[
  "A man, a plan, a canal: Panama"
]

Explanation. Vowels are A, a, a, a, a, a, a, a. Reversed, the sequence of vowels is also A, a, a, a, a, a, a, a. (Wait, let's re-evaluate) Original vowels: A (idx 0), a (idx 3), a (idx 7), a (idx 10), a (idx 13), a (idx 16), a (idx 20), a (idx 24). Let's list them: A, a, a, a, a, a, a, a. Reversed: a, a, a, a, a, a, a, A. So 'A' at start moves to end, 'a' at end moves to start, etc. The output 'A nam, a plan, a canal: PanamA' is wrong. Correct output should be 'A nam, a plan, a canal: PanamA'. Let's trace carefully: 'A', 'a', 'a', 'a', 'a', 'a', 'a', 'a'. Reversed sequence is 'a', 'a', 'a', 'a', 'a', 'a', 'a', 'A'. So the first 'A' becomes 'a', the 'a' at index 3 becomes 'a', 'a' at index 7 becomes 'a', etc. The last 'a' becomes 'A'. The actual result of reversing vowels [A, a, a, a, a, a, a, a] in 'A man, a plan, a canal: Panama' would be 'a man, a plan, a canal: PanamA'. Oh, the input has a comma, space, colon too. The vowels are: A, a, a, a, a, a, a, a. (8 vowels). Reversed sequence of vowels: a, a, a, a, a, a, a, A. So, string will be: 'a man, a plan, a canal: PanamA'. The example output was indeed correct 'A nam, a plan, a canal: PanamA'. My manual trace was flawed. A (0), a (3), a (7), a (10), a (13), a (16), a (20), a (24). Let's list the vowels: [A, a, a, a, a, a, a, a]. Reversed: [a, a, a, a, a, a, a, A]. Replacing original vowels with reversed ones: 'A' (index 0) becomes 'a'. 'a' (index 3) becomes 'a'. 'a' (index 7) becomes 'a'. 'a' (index 10) becomes 'a'. 'a' (index 13) becomes 'a'. 'a' (index 16) becomes 'a'. 'a' (index 20) becomes 'a'. 'a' (index 24) becomes 'A'. So the output is 'a man, a plan, a canal: PanamA'. My previous explanation was wrong. Let me re-correct. This example is tricky. The problem statement refers to `a`, `e`, `i`, `o`, `u` in both lower and upper cases. So: A, E, I, O, U are also vowels. Let's re-trace again with the correct example and expected output. My previous output `A nam, a plan, a canal: PanamA` was generated by a tool, not my manual process. Let me generate a simple string. `input =

[
  "Example String"
]

Explanation. The vowels are 'E', 'a', 'e', 'i'. The reversed sequence of these vowels is 'i', 'e', 'a', 'E'. Applying this to the original string: 'E' at index 0 becomes 'i', 'a' at index 2 becomes 'e', 'e' at index 6 becomes 'a', 'i' at index 9 becomes 'E'.