public decimal CalculateTotal(Trolley trolley)
{
var purchaseCosts = trolley.Purchases.Select(purchase =>
{
var pricingList = GetPricingList(trolley, purchase.Name);
// Initial State
var possibleTotals = new List <decimal>();
var lowestPriceQuantitiesSoFar = new Dictionary <int, decimal>();
var subtotals = new List <QuantityPrice>();
subtotals.Add(new QuantityPrice(purchase.Quantity, 0));
var newSubtotals = new List <QuantityPrice>();
while (subtotals.Count > 0)
{
// Map
foreach (var priceQuantity in pricingList)
{
var nextSubtotals = subtotals.Select(subtotal => new QuantityPrice(subtotal.Quantity - priceQuantity.Key, subtotal.Price + priceQuantity.Value));
newSubtotals.AddRange(nextSubtotals);
}
;
// Reduce
possibleTotals.AddRange(newSubtotals.Where(ns => ns.Quantity == 0).Select(ns => ns.Price));
newSubtotals.RemoveAll(ns => ns.Quantity <= 0);
newSubtotals = newSubtotals.GroupBy(ns => ns.Quantity, (key, result) => new QuantityPrice(key, result.Select(r => r.Price).Min())).ToList();
// Increment
subtotals = newSubtotals;
newSubtotals = new List <QuantityPrice>();
}
return(possibleTotals.Min());
});
return(purchaseCosts.Sum());
}
public Dictionary <int, decimal> GetPricingList(Trolley trolley, string productName)
{
var discounts = trolley.Discounts.Where(s => s.Name == productName);
var product = trolley.Products.Single(p => p.Name == productName);
var pricingList = new Dictionary <int, decimal>();
pricingList.Add(1, product.Price);
foreach (var discount in discounts)
{
if (pricingList.ContainsKey(discount.Quantity))
{
pricingList[discount.Quantity] = Math.Min(discount.Price, pricingList[discount.Quantity]);
}
else
{
pricingList.Add(discount.Quantity, discount.Price);
}
}
return(pricingList);
}