Reverse vowels of a string

Two Pointers String

60.7% acceptance

Jan 12, 2026

5325

2858

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.

Solution

Rust

Time O(n²)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn reverse_vowels(s: String) -> String {
    let mut chars: Vec<char> = s.chars().collect();
    let mut left = 0;
    let mut right = chars.len() - 1;
    
    let is_vowel = |c: char| -> bool {
      matches!(c, 'a' | 'e' | 'i' | 'o' | 'u' | 'A' | 'E' | 'I' | 'O' | 'U')
    };
    
    while left < right {
      while left < right && !is_vowel(chars[left]) {
        left += 1;
      }
      while left < right && !is_vowel(chars[right]) {
        right -= 1;
      }
      if left < right {
        chars.swap(left, right);
        left += 1;
        right -= 1;
      }
    }
    
    chars.into_iter().collect()
  }
}