private static bool ContainsRequiredColour(
IReadOnlyDictionary <string, ColouredBag> bagRules,
HashSet <string> containsColour,
ColouredBag bagRule,
string requiredColour)
{
if (containsColour.Contains(requiredColour))
{
return(true);
}
var mayContainRequiredColour = false;
if (bagRule.RequiredInnerBags.Count == 0)
{
mayContainRequiredColour = false;
}
else if (bagRule.RequiredInnerBags.ContainsKey(requiredColour))
{
mayContainRequiredColour = true;
}
else
{
foreach (var innerBagRule in bagRule.RequiredInnerBags)
{
var innerBagPermits = ContainsRequiredColour(
bagRules, containsColour, bagRules[innerBagRule.Key], requiredColour);
mayContainRequiredColour |= innerBagPermits;
if (innerBagPermits)
{
break;
}
}
}
return(mayContainRequiredColour);
}
public static void Solve()
{
var inputs = Tools.GetInput(7);
var bagRules = new Dictionary <string, ColouredBag>();
foreach (var ruleDefinition in inputs)
{
var bag = new ColouredBag(ruleDefinition);
bagRules[bag.Colour] = bag;
}
// Part 1.
var coloursThatMayContainShinyGold = new HashSet <string>();
ContainsRequiredColour(bagRules, coloursThatMayContainShinyGold, "shinygold");
var permittedColours = string.Concat(coloursThatMayContainShinyGold.Select(s => $"{s}, "));
Console.WriteLine($"May contain ShinyGold = {coloursThatMayContainShinyGold.Count}. {permittedColours}");
// Part 2.
var bagsRequiredForShinyGold = RequiredBags(bagRules, new Dictionary <string, int>(), "shinygold");
Console.WriteLine($"Bags required for ShinyGold = {bagsRequiredForShinyGold}. (Including ShinyGold one too).");
}