Reverse Vowels of a String

Problem Summary

• Given a string, reverse just the vowels in it

Key Observations

• Solve it in $O(n)$ time and space

Main Concepts Used

• Strings
• Two Pointers#1. Opposite Direction Pointers (Start–End)

Time & Space Complexity

• Time: $O()$ → Reason:
• Space: $O()$ → Reason:

Code

class Solution:
    def reverseVowels(self, s: str) -> str:
        vowels = ["a", "e", "i", "o", "u"]
        l, r = 0, len(s) - 1
        word = list(s)

        while l < r:
            if word[l].lower() not in vowels:
                l += 1
                continue
            if word[r].lower() not in vowels:
                r -= 1
                continue

            word[l], word[r] = word[r], word[l]
            l += 1
            r -= 1
        return "".join(word)

Common Mistakes / Things I Got Stuck On