/// <summary>
/// Given a permutation tree, we will convert each branch path into a list of cards represnting a unique permutation.
/// </summary>
/// <param name="permutations">List of permutations</param>
/// <param name="node">Tree root</param>
/// <param name="cardStack">Card stack for keeping track of branches</param>
private static void BuildCardPermutationList(List<List<ProgramCardType>> permutations, PermutationNode node, Stack<ProgramCardType> cardStack = null)
{
if (node == null)
throw new ArgumentNullException("node");
if (permutations == null)
throw new ArgumentNullException("permutations");
cardStack = cardStack ?? new Stack<ProgramCardType>(5);
if (cardStack.Count == Constants.RobotRegisters || node.Children == null)
{
var p = new List<ProgramCardType>(cardStack);
p.Reverse();
permutations.Add(p);
return;
}
foreach (var child in node.Children)
{
if (child.Card == null)
{
throw new InvalidOperationException();
}
cardStack.Push(child.Card.Value);
BuildCardPermutationList(permutations, child, cardStack);
cardStack.Pop();
}
}
/// <summary>
/// Calculate all possible move permutations given a robots set of cards
/// </summary>
/// <param name="robot">Robot</param>
/// <returns>List of permutations</returns>
internal static List<List<ProgramCardType>> CalculateMovePermutations(Robot robot)
{
var permutations = new List<List<ProgramCardType>>();
// This is the list of cards that can be placed. Locked registers are not included in this list
// and should be appended to the end of each list if necessary
IEnumerable<ProgramCardType> cards = robot.CardsToPlace().Select(ProgramCard.GetCardTypeByPriority);
var root = new PermutationNode();
BuildCardPermutationTree(root, cards);
BuildCardPermutationList(permutations, root);
return permutations;
}
private static void BuildCardPermutationTree(PermutationNode node, IEnumerable<ProgramCardType> cardsToPlace, int depth = Constants.RobotRegisters)
{
if (depth == 0)
return;
var children = new List<PermutationNode>();
var cards = new List<ProgramCardType>(cardsToPlace);
var distinctCards = new List<ProgramCardType>(cards.Distinct());
foreach (var distinctCard in distinctCards)
{
var child = new PermutationNode {Card = distinctCard};
var remainingCards = new List<ProgramCardType>(cards);
remainingCards.Remove(distinctCard);
BuildCardPermutationTree(child, remainingCards, depth - 1);
children.Add(child);
}
node.Children = children;
}