10866.js

// https://www.acmicpc.net/problem/10866
const filePath = process.platform === 'linux' ? 0 : 'input.txt';
const input = require('fs').readFileSync(filePath).toString().split('\n');

const N = Number(input.shift());

class Deque {
  constructor() {
    this._arr = [];
  }
  push_front(data) {
    this._arr.unshift(data);
  }
  push_back(data) {
    this._arr.push(data);
  }
  size() {
    return this._arr.length;
  }
  pop_front() {
    return this.size() === 0 ? -1 : this._arr.shift();
  }
  pop_back() {
    return this.size() === 0 ? -1 : this._arr.pop();
  }
  empty() {
    return this.size() === 0 ? 1 : 0;
  }
  front() {
    return this.size() === 0 ? -1 : this._arr[0];
  }
  back() {
    return this.size() === 0 ? -1 : this._arr[this.size() - 1];
  }
}

function solution(n, input) {
  const deque = new Deque();
  let result = [];
  for (let i = 0; i < n; i++) {
    let command = input[i].split(' ')[0];
    switch (command) {
      case 'push_back':
        deque.push_back(Number(input[i].split(' ')[1]));
        break;
      case 'push_front':
        deque.push_front(Number(input[i].split(' ')[1]));
        break;
      case 'pop_front':
        result.push(deque.pop_front());
        break;
      case 'pop_back':
        result.push(deque.pop_back());
        break;
      case 'size':
        result.push(deque.size());
        break;
      case 'empty':
        result.push(deque.empty());
        break;
      case 'front':
        result.push(deque.front());
        break;
      case 'back':
        result.push(deque.back());
    }
  }
  return result.join('\n');
}
console.log(solution(N, input));