LeetCode 1119. Remove Vowels from a String

Problem Statement

use std::collections::HashSet;
use std::iter::FromIterator;
impl Solution {
    pub fn remove_vowels(s: String) -> String {
        let (mut ans, mut j) = ("".to_string(), 0);
        let vowel_set : HashSet<char> = HashSet::from_iter(vec!['a', 'e', 'i', 'o', 'u']);
        while j < s.len() {
            let sj = s.chars().nth(j).unwrap();
            if !vowel_set.contains(&sj) {
                ans.push(sj);
            }
            j+= 1;
        }
        return ans;
    }
}