print directory problem

// https://www.typescriptlang.org/play?#code/C4TwDgpgBAIglgJwgY2AewSKBeKBvAKCmKgG0BrCEALigGdgE4A7AcwF1b4lUMsAfKMwCuAG1EBuAgF8CBZGmYMoLMMOA4yREgHIA9AAs0AWwh6AhmDAWrARh0AabcX1HTN65bAAmR86iuJmZeHgDMfiQBhkF66nCidLHA8fZOkYHucQlJ8b5putHuIV4ALI5QenpQEAAmrNDI5nQQtMAG0KrqKnRCaBp0GMC1UCAQwP4ZZiw1EAAeAHQAVnR+7FIElVBt0IwQ0HRGYjVQomho5CdwlFsGcHTyiso1iFyIKOiYmoSRbi34-pEvLRvpFQcQvLZaCJxPkwYCrN4oWJRLC4eCrKEkTCAXDSliUTjiNJUZEsnRgYTQVlIUJkSS4VlEbTsWjiZSdNM5ksVvj-LJZAQAGbCZioOCKKAAI2E8Rq3HefAAKkgIAAKMDmNrk+iMFisUjsACUrx4HywIOICiUGl2f3lvE+uDw0nWkQ1WvmgowAFFzMgDKr1ZqDIacAA+f5oq3KDUIYA9XDugzzOiiODINW2Q0psBp4Cq-Q6Q2uuGiMZQZDCBBIZjAAByaBmmltJbBsfjnp9foDQbjoewEYtaJUgqgqoAhJXqxBaw2ZqR20bI8OwVOa-XGxAF+Y4+wvi7KZFZCvLVX13PoLg1zON-PF1AmrA3g6QFJWcW+R--EhgFXmFsVSkAVhVFZIJS9BBjE1e0zWVPZVVtE0FUwBwTggAA3CBRCRYxJQgBBNAABmNHUmDYZdiDLDQkDoMQNFwHQdFbKAILHaMNEoLAWAAvZQyHSJ2JUZgZlrTQdAAWh0eYkEgTVVTLTDRA-NEaLoqAAGpcAAAwAEjwTla2kcS9M46QAB1mC05iBMeDR-VlC9mxVCgqDWSk4FHVV7NEGoLz4w8SFU0QNE0liMCg4AYKVFUvNuHyL1QhSsI0qAszfOFjxIAVIh-P8oCC4AgLkQTnlNaK9k0aVZSizA4LVTpgA-QSIIioYagAeXUNR6LCyDoOfWCYtK5CQDqprHjQMt5lOVgCwsnQUpazU2s64BuuLIA

type Directory = {
    [key: string]: Directory | null;
}

const input = [
    '/home/app/app1',
    '/home/app/app2',
    '/home/app/app3',
    '/home/utils/util1',
    '/home/utils/util2',
    '/home/app/app4', // edge case: the input is not sorted yet
    '/home/index.js',
];

// the tree should look like this
const dir: Directory = {
    home: {
        app: {
            app1: null,
            app2: null,
            app3: null,
            app4: null,
        },
        utils: {
            util1: null,
            util2: null,
        },
        'index.js': null
    }
}

function buildDirectoryTree(paths: string[]): Directory {
    const tree: Directory = {};

    paths.forEach((path) => {
        const parts = path.slice(1).split('/');

        let currentNode = tree;

        parts.forEach((part) => {
            if (!currentNode[part]) {
                currentNode[part] = {};
            }
            currentNode = currentNode[part] as Directory;
        });
    });

    return tree;
}

function formatDirectoryTree(tree: Directory, level: number = 0): string {
    let result = '';

    for (const key in tree) {
        const indent = '-'.repeat(level);
        result += `${indent}-${key}\n`;

        const childNode = tree[key];
        if (childNode) {
            result += formatDirectoryTree(childNode, level + 1);
        }
    }

    return result;
}

const directoryTree = buildDirectoryTree(input);
const formattedOutput = formatDirectoryTree(directoryTree);
console.log('\n' + formattedOutput);

https://en.wikipedia.org/wiki/Trie