private (int winner, long score) PlayRecursiveCombat_WithHashing(IEnumerable <int> deck1cards,
IEnumerable <int> deck2cards)
{
var deck1 = new HashQueue(deck1cards);
var deck2 = new HashQueue(deck2cards);
var cache = new HashSet <(long, long)>();
int GetRoundWinner(int card1, int card2)
{
if (card1 <= deck1.Count && card2 <= deck2.Count)
{
return(PlayRecursiveCombat_WithHashing(deck1.Take(card1), deck2.Take(card2)).winner);
}
return(card1 > card2 ? 1 : 2);
}
while (deck1.Any() && deck2.Any())
{
var state = (deck1.Hash, deck2.Hash);
if (!cache.Add(state))
{
return(1, GetWinnerScore(deck1, deck2));
}
var card1 = deck1.Dequeue();
var card2 = deck2.Dequeue();
var winner = GetRoundWinner(card1, card2);
var winnerDeck = winner == 1 ? deck1 : deck2;
winnerDeck.Enqueue(winner == 1 ? card1 : card2);
winnerDeck.Enqueue(winner == 1 ? card2 : card1);
}
return(winner: deck1.Any() ? 1 : 2, GetWinnerScore(deck1, deck2));
}