Remove Sub-Folders from the Filesystem

function removeSubfolders(folders: string[]): string[] {
  const set = new Set(folders);
  return folders.filter((folder) => !isSubFolder(set, folder));
}
 
function isSubFolder(set: Set<string>, folder: string) {
  let endIndex = folder.lastIndexOf('/');
  while (0 < endIndex) {
    const prefix = folder.substring(0, endIndex);
    if (set.has(prefix)) {
      return true;
    }
    endIndex = prefix.lastIndexOf('/');
  }
  return false;
}

function removeSubfolders(folders: string[]): string[] {
  folders.sort();
  const result = [folders[0]];
  for (let i = 1; i < folders.length; i++) {
    const lastFolder = `${result[result.length - 1]}/`;
    if (!folders[i].startsWith(lastFolder)) {
      result.push(folders[i]);
    }
  }
  return result;
}

export function removeSubfolders(folders: string[]): string[] {
  const trie = new Trie(folders);
  return folders.filter((folder) => !trie.isSubFolder(folder));
}
 
class TrieNode {
  readonly children: Map<string, TrieNode>;
  public isEnd: boolean;
  constructor() {
    this.children = new Map();
    this.isEnd = false;
  }
 
  getChildNode(folder: string): TrieNode {
    const childNode = this.children.get(folder);
    if (childNode) {
      return childNode;
    }
    const newNode = new TrieNode();
    this.children.set(folder, newNode);
    return newNode;
  }
}
 
class Trie {
  private readonly root: TrieNode;
  constructor(folders: string[]) {
    this.root = new TrieNode();
    for (const folder of folders) {
      this.addFolder(folder);
    }
  }
 
  private getFolderNames(folder: string) {
    return folder.split('/').slice(1);
  }
 
  addFolder(folder: string) {
    let currentNode = this.root;
    for (const folderName of this.getFolderNames(folder)) {
      currentNode = currentNode.getChildNode(folderName);
    }
    currentNode.isEnd = true;
  }
 
  isSubFolder(folder: string) {
    let currentNode = this.root;
    for (const folderName of this.getFolderNames(folder)) {
      if (currentNode.isEnd) {
        return true;
      }
      currentNode = currentNode.getChildNode(folderName);
    }
    return false;
  }
}