A counter keeping track of multiple values inside an array

arrays, combinations, counter, javascript

Solution

Basically this proposal relies on a function to get the next items

    getItems = function () {
        var price = 0,
            array = lottery.map(function (a) { return a.price; });

        return function () {
            var items;
            do {
                items = combine(array, price);
                price++;
            } while (!items.length)
            return items;
        }
    }(),

which starts at price with zero and increments the value by one until a combination of items is found. Then the `items` array is returned. The function works as generator.

The other important function is the combination of items with a given price and the try to get an array with the items.

function combine(array, sum) {

    function c(left, right, sum) {
        if (!sum) {
            result = right;
            return true;
        }
        return left.some(function (a, i, aa) {
            return a <= sum && c(aa.slice(i + (a > sum - a)), right.concat(a), sum - a);
        });
    }

    var result = [];
    c(array.sort(function (a, b) { return b - a; }), [], sum);
    return result;
}

`combine` takes an array with prices and a wanted sum to reach with combinating the given prices. If successfull, an array with the items is returned, otherwise an empty array.

The third part is to use the items as long as the investment is not negative. If that happens, a new items set is fetched.

function combine(array, sum) {

    function c(left, right, sum) {
        if (!sum) {
            result = right;
            return true;
        }
        return left.some(function (a, i, aa) {
            return a <= sum && c(aa.slice(i + (a > sum - a)), right.concat(a), sum - a);
        });
    }

    var result = [];
    c(array.sort(function (a, b) { return b - a; }), [], sum);
    return result;
}

var lottery = [{ name: 'twig', price: 5, win: 40 }, { name: 'rock', price: 10, win: 80 }, { name: 'shell', price: 28, win: 250 }, { name: 'chip', price: 50, win: 400 }, { name: 'gold', price: 56, win: 500 }, { name: 'diamond', price: 280, win: 2500 }],
    lotteryByPrice = lottery.reduce(function (r, a) { r[a.price] = a; return r; }, Object.create(null)),
    getItems = function () {
        var price = 0,
            array = lottery.map(function (a) { return a.price; });

        return function () {
            var temp;
            do {
                temp = combine(array, price);
                price++;
            } while (!temp.length)
            return temp;
        }
    }(),
    createTableRow = function (element) {
        var table = document.createElement('table'),
            tr = document.createElement('tr');

        ['Game', 'Items', 'Types', 'Spend Per Game', 'Total Spend', 'Max. Possible Winnigs', 'Investment'].forEach(function (a) {
            var th = document.createElement('th');
            th.appendChild(document.createTextNode(a));
            tr.appendChild(th);
        });
        table.appendChild(tr);
        element.appendChild(table);

        return function (row) {
            var tr = document.createElement('tr');
            ['game', 'items', 'types', 'spend', 'total', 'potential', 'investment'].forEach(function (k) {
                var td = document.createElement('td');
                td.appendChild(document.createTextNode(row[k]));
                tr.appendChild(td);
            });
            if (row.topBorder) {
                tr.style.borderTop = '2px solid #666';
            }
            table.appendChild(tr);
        };
    }(document.body),
    row = { game: null, items: null, types: null, spend: null, total: 0, potential: null, investment: null },
    i,
    items = getItems(),
    add = function (a, b) { return a + b; },
    winP = function (a) { return lotteryByPrice[a].win; },
    nameP = function (a) { return lotteryByPrice[a].name; };

for (i = 1; i <= 70; i++) {
    row.topBorder = false;
    while (row.total - items.reduce(add) + items.map(winP).reduce(add) < 0) {
        items = getItems();
        row.topBorder = true;
    }
    row.game = i;
    row.items = items.length;
    row.types = items.map(nameP).join(' + ');
    row.spend = -items.reduce(add);
    row.total += row.spend;
    row.potential = items.map(winP).reduce(add);
    row.investment = row.potential + row.total;
    createTableRow(row);
}

table { border-collapse: collapse; font-family: Sans-Serif; }
th { border: 1px solid #ccc; padding: 0 10px; }
td { text-align: center; border: 1px solid #ccc; }

Problem

Original source