HackerRank.com Challenge #2 (SpaceX) Solution in NodeJS

hackerchallenge2-spacex.js

//
// HackerRank.com Challenge #2 (SpaceX Challenge)
// @hacker mediaupstream, aka Derek Anderson
//
// How to Win:
// 1. Install required npm packages: `npm install request sugar`
// 2. Modify the `username` and `password` variables below to match what you used to signup on
// hackerrank.com with
// 3. Run the script: `$ node hackerchallenge2-spacex.js`
// 4. Wait for about 40 minutes...
// 
// The script can be optimized to run each game in parallel, probably.
//
var request = require('request'),
    username = 'USERNAME HERE',
    password = 'PASSWORD HERE',
    gameStart = 1,
    gameEnd = 10000;

    // I am lazy, and sugar is sweet.
    require('sugar');

//
// Quick lookup for our ghetto lexical parser
//
var tokens = {
  zero: 0, one: 1, two: 2, three: 3, four: 4, five: 5, six: 6, seven: 7, eight: 8, nine: 9,
  ten: 10, eleven: 11, twelve: 12, thirteen: 13, fourteen: 14, fifteen: 15, sixteen: 16,
  seventeen: 17, eighteen: 18, nineteen: 19, twenty: 20, thirty: 30, fourty: 40, fifty: 50,
  sixty:60, seventy: 70, eighty: 80, ninety:90
};

//
// Ghetto lexical parser, transforms phrases into numbers
// eg: "one thousand two hundred and six" becomes "1206"
//
var parseWords = function(str){
  str = str.replace(',', '').replace('-', ' ').replace(' and', '').split(' ');
  var results = [];
  for(var i=0; i<str.length; i++){
    var cur = str[i];
    if(cur.has(/hundred|thousand|million|billion|trillion/)) continue;
    var num = tokens[cur];
    var next = str[i+1];
    if(next){
      if(next.has('hundred'))  num += '00';
      if(next.has('thousand')) num += '000';
      if(next.has('million'))  num += '00000';
      if(next.has('billion'))  num += '00000000';
    }
    results.push(num);
  }
  var sum = results.sum(function(n){
    return parseInt(n, 10);
  });
  return sum;
};


//
// Decrypts a `string`, using ROT13 style encryption, given the `num` number offset
//
// @param {string} string The encrypted string, eg: 'lbhe zbz'
// @param {number} num The number offset to "shift" the `string` by
// @param {boolean} enc (optional) true to encrypt rather than decrypt
//
var decrypt = function(string, num, enc){
  // dictionary of character codes, the numeric values of our ascii characters.
  var dict = [
    'abcdefghijklmnopqrstuvwxyz'.codes(),
    'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.codes()
  ];
  var buf = ''; // our encrypted / decrypted message will go here
  // loop over our string, one character at a time
  for(var i=0; i<string.length; i++){
    var c = string.charCodeAt(i); // the current character code
    var o = (c >= 97) ? dict[0] : dict[1]; // which dict to use
    var index = o.findIndex(c); // index of the character in dict
    var n = c; // encrypted / decrypted character code
    if(c != 32 && c != 45 && c != 44){ // skip "space" "," and "-" chars
      index = (!enc) ? (index-num) : (index+num); // shift up or down based on `enc`
      // get the new character from our dictionary, given the shifted index from above
      n = o.at(index, true); 
    }
    // transform the number (n) into the character code (eg, "A")
    // and append it to our buffer, which in turn will start to spell out the
    // decrypted / encrypted message
    buf += (n).chr();
  }
  return buf;
};

//
// Wrapper to decrypt with the `enc` flag set to true
//
var encrypt = function(string, num){
  return decrypt(string, num, true);
};

//
// Log into HackerRank.com using the Request module
//
var login = function(username, pass, cb){
  request({
    url: 'https://www.hackerrank.com/users/sign_in',
    form: {
      'commit': 'Sign in',
      'user[login]': username,
      'user[password]': pass,
      'user[remember_me]': 1
    },
    method: 'POST'
  }, cb);
};

//
// Ask HackerRank.com for a game
// @param {number} n The number of game you want in the range 1-10000
// @param {function} cb A callback with response data
//
var getGame = function(n, cb){
  request({
    url: 'https://www.hackerrank.com/game.json',
    method: 'POST',
    form: {
      n: n,
      remote: true
    }
  }, cb);
};

//
// Helper method to submit an answer to HackerRank.com
// @param {object} d This object should be in the format:
//    {
//      id: 12943, // the game ID, not the same as the game number, eg 1-10000
//      answer: 102, // your answer
//      remote: true
//    }
//
var submitAnswer = function(d, cb){
  request({
    url: 'https://www.hackerrank.com/game.json',
    method: 'PUT',
    form: d
  }, cb);
};

//
// Crack an encrypted string
//
// we are taking advantage of the fact that all decrypted messages
// will contain lexical numbers, eg: "twelve", in essence a brute-force rot13
//
// @param {string} str The encrypted string to decrypt
// @returns {string} a decrypted string
//
var crack = function(str){
  var result = '';
  for(var i=0; i<35; i++){
    var test = decrypt(str, i);
    // console.log(test);
    if(test.has(/thousand|hundred|and|zero|one|two|three|four|five|six|seven|eight|nine|ten/) ||
       test.has(/eleven|twelve|thirteen|fourteen|fifteen|sixteen|seventeen|eighteen|nineteen/) ||
       test.has(/twenty|thirty|fourty|fifty|sixty|seventy|eighty|ninety/) ){
      result = test;
      break;
    }
  }
  return result;
};

//
// Crack the whole game, from range `start` to `stop`
// Also submits the answer, so you'll want to login first before calling this...
//
var crackAll = function(start, stop){
  start = start || 1;
  stop  = stop || 10000;
  console.log('cracking '+ start +' to '+ stop +'... this will take awhile.');
  for(var i=start; i<=stop; i++){
    (function(level){
      getGame(level, function(x,y, body){
        // something went wrong... probably a server request limiting issue
        if(body.has('<')) return console.log('Something went wrong on game #'+ level);
        // all is well... process
        body = JSON.parse(body);
        if(body && body.game && body.game.cph_number){
          var answer = crack(body.game.cph_number);
          var number = parseWords( answer );
          console.log('Message: '+ answer +', Number: '+ number);
          if(isNaN( number )){
            console.log('- Error');
            console.log(level);
            console.log(body.game.cph_number);
            console.log(answer);
            console.log(number);
          } else {
            submitAnswer({
            id: body.game.id,
            answer: number,
            remote: true
            }, function(x,y, resp){
              if(!resp.has('Congrats')){
                console.log('===');
                console.log('incorrect answer: '+ level);
                console.log(body.game.cph_number);
                console.log(answer);
                console.log(number);
              }
            });
          }
        }
      });
    })(i);
  }
};

//
// login to hackerrank.com and start crackin'
//
login(username, password, function(err, res, body){
  crackAll(gameStart, gameEnd);
});