Is Reverse Vowels of a String easy or hard?

Reverse Vowels of a String is classified as an Easy problem. The main challenge is recognizing the two-pointer pattern and correctly skipping non-vowel characters while performing swaps.

Reverse Vowels of a String Python/Java solution

In Python or Java, convert the string to a mutable character array, maintain two pointers, and swap vowels when both pointers encounter them. The algorithm runs in O(n) time and uses constant extra space with the two-pointer approach.

How to solve Reverse Vowels of a String in O(n)?

Use two pointers starting from the left and right ends of the string. Move each pointer until it reaches a vowel, swap the characters, and continue moving inward. Since each index is processed only once, the total runtime remains linear O(n).

What is the best approach for Reverse Vowels of a String?

The two pointers approach is the most efficient solution. Place one pointer at the start of the string and another at the end, move them inward until vowels are found, and swap them. This method processes the string once with O(n) time and O(1) extra space.

Is Reverse Vowels of a String asked at Google/Amazon/Meta?

Reverse Vowels of a String is a common string manipulation problem seen in interview preparation lists and coding practice platforms. Variants of two-pointer string problems appear frequently in interviews at companies like Amazon, Google, and Meta.

What data structure is used in Reverse Vowels of a String?

The optimal approach primarily uses the two-pointer technique with a small lookup structure (such as a set or string) to check whether a character is a vowel. Alternative implementations may use a stack to store vowels before placing them back in reverse order.

What is the time complexity of Reverse Vowels of a String?

The optimal algorithm runs in O(n) time because each character in the string is visited at most once while moving the two pointers inward. Space complexity can be O(1) for the in-place two-pointer approach or O(n) if a stack is used to store vowels.

345. Reverse Vowels of a String - Practice Online

Given a string s, reverse only all the vowels in the string and return it.

The vowels are 'a', 'e', 'i', 'o', and 'u', and they can appear in both lower and upper cases, more than once.

Example 1:

Input: s = "IceCreAm"

Output: "AceCreIm"

Explanation:

The vowels in s are ['I', 'e', 'e', 'A']. On reversing the vowels, s becomes "AceCreIm".

Example 2:

Input: s = "leetcode"

Output: "leotcede"

Constraints:

1 <= s.length <= 3 * 10⁵
s consist of printable ASCII characters.