31. 模拟目录管理功能

const readline = require('readline');
const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
});

class Node {
    constructor(path, parent) {
        this.path = path;
        this.next = {};
        if (parent) {
            this.next['..'] = parent;
        }
    }
}
function isValidDirectoryName(name) {
    return /^[a-z]+$/.test(name);
}
function isValidChangeDirectory(name) {
    return name === '..' || isValidDirectoryName(name);
}
let root = new Node('/', null);
let currentNode = root;
let lastoutput = '';
rl.on('line', (line) => {
    const parts = line.split(' ');
    const command = parts[0];
    if (command === 'mkdir' && parts.length === 2 && isValidDirectoryName(parts[1])) {
        if (!currentNode.next[parts[1]]) {
            currentNode.next[parts[1]] = new Node(currentNode.path+parts[1]+'/', currentNode) 
        }
    } else if (command === 'cd' && parts.length === 2 && isValidChangeDirectory(parts[1])) {
        const nextNode = currentNode.next[parts[1]];
        if (nextNode) {
            currentNode = nextNode;
        }
    } else if (command === 'pwd' && parts.length === 1) {
        lastoutput = currentNode.path;
        console.log(lastoutput);
    }
});