einstein riddle solver

README.md

Einstein Riddle solver

http://www.theguardian.com/science/alexs-adventures-in-numberland/2015/may/04/einsteins-election-riddle-are-you-in-the-two-per-cent-that-can-solve-it

solution.sh

#!/usr/bin/env node

var assert = require('assert');

var houses = [
  'polka dot',
  'tartan',
  'gingham',
  'paisley',
  'striped'
];

var people = [
  'nicola',
  'nigel',
  'david',
  'ed',
  'nick'
];

var pets = [
  'squirrel',
  'fish',
  'guinnea pig',
  'pitbull',
  'badger'
];

var coffees = [
  'flat whites',
  'double espresso',
  'chai latte',
  'decaf',
  'mochaccino'
];

var transports = [
  'car',
  'plane',
  'foot',
  'train',
  'bike'
];

function randomOrder (arr) {
  var arrCopy = arr.slice();
  arrCopy.sort(function (a, b) {
    return Math.random() >= 0.5 ? 1 : -1;
  });
  return arrCopy;
}

function newCandidate () {
  var data = {
    houses: houses,
    people: people.slice(),
    pets: pets.slice(),
    coffees: coffees.slice(),
    transports: transports.slice()
  };

  function randomChoice (type) {
    var len = data[type].length;
    var idx = Math.ceil(Math.random() * len) - 1;
    if (idx === -1) idx = 0;
    if (typeof data[type][idx] === 'undefined') throw new Error('undefined idx: ' + type + ', ' + idx);
    var choice = data[type].splice(idx, 1)[0];
    return choice;
  }

  return randomOrder(houses).map(function (house, idx) {
    return {
      house: house,
      houseIdx: Number(idx),
      person: randomChoice('people'),
      pet: randomChoice('pets'),
      coffee: randomChoice('coffees'),
      transport: randomChoice('transports')
    };
  });
}

var solution;
do {
  var c = newCandidate();
  function find (val) {
    var house;
    for (var idx = 0; idx < c.length; idx++) {
      Object.keys(c[idx]).forEach(function (k) {
        if (c[idx][k] == val) house = c[idx];
      });
    }
    if (!house) throw new Error('could not find val: ' + val);
    return house;
  }
  try {
    // 1
    var nicola = find('nicola');
    assert.equal(nicola.house, 'tartan');
    
    // 2
    var ed = find('ed');
    assert.equal(ed.pet, 'guinnea pig');

    // 3
    var david = find('david');
    assert.equal(david.coffee, 'mochaccino');

    // 4
    var paisley = find('paisley');
    var gingham = find('gingham');
    assert.equal(gingham.houseIdx - 1, paisley.houseIdx);

    // 5
    assert.equal(paisley.coffee, 'flat whites');

    // 6
    var car = find('car');
    assert.equal(car.pet, 'squirrel');

    // 7
    var striped = find('striped');
    assert.equal(striped.transport, 'bike');

    // 8
    var centre = c[2];
    assert.equal(centre.coffee, 'double espresso');

    // 9
    var nick = find('nick');
    assert.equal(nick.houseIdx, 0);

    // 10
    var train = find('train');
    var pitbull = find('pitbull');
    assert.equal(Math.abs(train.houseIdx - pitbull.houseIdx), 1);

    // 11
    var badger = find('badger');
    var bike = find('bike');
    assert.equal(Math.abs(badger.houseIdx - bike.houseIdx), 1);

    // solved in 2m

    // 12
    var chai = find('chai latte');
    // assert.equal(chai.transport, 'plane');

    // 13
    var nigel = find('nigel');
    assert.equal(nigel.transport, 'foot');

    solution = c;
    break;

    // 14
    var polka = find('polka dot');
    assert.equal(Math.abs(nick.houseIdx - polka.houseIdx), 1);

    // 15
    var decaf = find('decaf');
    assert.equal(Math.abs(train.houseIdx - decaf.houseIdx), 1);

    solution = c;
  }
  catch (e) {}
}
while (!solution);

console.log(JSON.stringify(solution, null, 2));