set-v2.js

Array.prototype.shuffle =  function() {
    var c = this.length, temp, i;
    while (c > 0) {
        i = Math.floor(Math.random() * c);
        c--;
        temp = this[c];
        this[c] = this[i];
        this[i] = temp;
    }
    return this;
};

function Deck(cards) {
    if (cards == null) {
        this.cards = Deck.CARDS.slice(0).shuffle();
    } else {
        this.cards = cards;
    }
}

Deck.CARDS = (function() {
    var list = [];
    for (var i = 0; i < 81; i++) {
        list.push([
            ~~(i / 27) % 3,
            ~~(i /  9) % 3,
            ~~(i /  3) % 3,
            ~~(i /  1) % 3
        ]);
    }
    return list;
}());


Deck.isSet = function(a, b, c) {
    for (var i = 0; i < 4; i++) {
        if (!(a[i] === b[i] && b[i] === c[i]) &&
            !(a[i] !== b[i] && a[i] !== c[i] && b[i] !== c[i])) {
            return false;
        }
    }
    return true;
};

Deck.prototype.deal = function(n, dest) {
    dest = dest || new Deck([]);
    for (var i = 0; i < n; i++) {
        dest.cards.push(this.cards[i]);
    }
    this.cards = this.cards.slice(n);
    return dest;
};

Deck.prototype.isEmpty = function() {
    return this.cards.length === 0;
};

Object.defineProperty(Deck.prototype, 'length', {
    get: function() {
        return this.cards.length;
    }
});

Deck.prototype.findSet = function() {
    var cards = this.cards, len = cards.length, result = false;
    for (var i = 0; i < len - 2; i++) {
        for (var j = i + 1; j < len - 1; j++) {
            for (var k = j + 1; k < len - 0; k++) {
                if (Deck.isSet(cards[i], cards[j], cards[k])) {
                    var set = [cards[i], cards[j], cards[k]];
                    this.cards = this.cards.filter(function(e, ii) {
                        return ii !== i && ii !== j && ii !== k;
                    });
                    return set;
                }
            }
        }
    }
    return null;
};

function Histo() {
    this.data = {};
}

Histo.prototype.increment = function(point) {
    if (this.data[point] == null) this.data[point] = 0;
    this.data[point]++;
};

function monteCarlo(n) {
    var histo = new Histo();
    for (var i = 0; i < n; i++) {
        var deck = new Deck(), dealt = deck.deal(9);
        while (!deck.isEmpty()) {
            deck.deal(3, dealt);
            while (dealt.findSet() != null) {};
            histo.increment(dealt.length);
        }
    }
    return histo;
}