Longest substring of all vowels in order

String Sliding Window

51.6% acceptance

Feb 25, 2026

850

A string is considered beautiful if it satisfies the following conditions: Each of the 5 English vowels ('a', 'e', 'i', 'o', 'u') must appear at least once in it. The letters must be sorted in alphabetical order (i.e. all 'a's before 'e's, all 'e's before 'i's, etc.). Given a string word consisting of English vowels, return the length of the longest beautiful substring of word. If no such substring exists, return 0.

Solution

Rust

Time O(n²)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn longest_beautiful_substring(word: String) -> i32 {
    let bytes = word.as_bytes();
    let n = bytes.len();
    let mut result = 0;
    let mut i = 0;
    while i < n {
      if bytes[i] != b'a' { i += 1; continue; }
      let start = i;
      let mut distinct = 1;
      i += 1;
      while i < n && bytes[i] >= bytes[i-1] {
        if bytes[i] > bytes[i-1] { distinct += 1; }
        i += 1;
      }
      if distinct == 5 {
        result = result.max(i - start);
      }
    }
    result as i32
  }
}