LeetCode 1233. Remove Sub-Folders from the Filesystem

Problem Statement

impl Solution {
    pub fn remove_subfolders(folder: Vec<String>) -> Vec<String> {
        let (mut f, mut ans) = (folder, vec![]);
        if f.is_empty() {
            return vec![];
        }
        f.sort();
        ans.push(f[0].clone());
        
        for i in 1..f.len() {
            let mut prefix = ans.last().unwrap().clone();
            prefix.push('/');
            let cur = f[i].clone();
            if cur.len() < prefix.len() || cur[..prefix.len()].to_string() != prefix  {
                ans.push(cur);
            }
        }
        return ans;
    }
}