Strategy FindWinningStrategy(Strategy strategy)
{
//Console.WriteLine("{0}", string.Join(" ", strategy.OpenedChests.Select(x=>x.Id)));
Debug.Assert(strategy.ClosedChests.Count() + strategy.OpenedChests.Count() == chests.Count());
if (!strategy.ContainsEnoughKeys || !strategy.CanReachAnyChest)
{
//Console.WriteLine("STOP");
return null;
}
if (!strategy.ClosedChests.Any())
{
// we have a winner...
return strategy;
}
var openeableChests = strategy.ClosedChests
.Where(chest => strategy.KeysInHand.Contains(chest.RequiredKey));
foreach (var chest in openeableChests)
{
var inner = FindWinningStrategy(strategy.OpenChest(chest));
if( inner != null )
return inner;
}
return null;
}
public object Solve()
{
var start = new Strategy(keys, Enumerable.Empty<Chest>(), chests);
var strategy = FindWinningStrategy(start);
if (strategy != null)
{
Debug.Assert(strategy.ClosedChests.Count() == 0);
Debug.Assert(strategy.OpenedChests.Count() == chests.Count());
Debug.Assert(strategy.OpenedChests.Distinct().Count() == chests.Count());
var remainingKeys = strategy.KeysInHand.Count();
var totalKeys = keys.Count() + chests.Sum(x => x.ContainedKeys.Count());
var expected = totalKeys - chests.Count();
Debug.Assert(remainingKeys == expected);
return string.Join(" ", strategy.OpenedChests.Select(x => x.Id));
}
else
{
return "IMPOSSIBLE";
}
}
