using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var monsterBone = new Resource{Id = 1, Name = "Monster Bone", Kind = ResourceKind.Bone, };

        var monsterHide = new Resource{Id = 2, Name = "Monster Hide", Kind = ResourceKind.Hide, };

        var monsterOrgan = new Resource{Id = 3, Name = "Monster Organ", Kind = ResourceKind.Organ, };

        var unicornFur = new Resource{Id = 4, Name = "Unicorn Fur", Kind = ResourceKind.Bone | ResourceKind.Hide, };

        var recipe = new Recipe

        {

            Resources = new Dictionary<ResourceKind, int>{{ResourceKind.Bone, 1}, {ResourceKind.Hide, 1}, }, 

            UniqueResources = new Dictionary<Resource, int>{{unicornFur, 1}}, 

        };

        { // we cannot

            var inventory = new List<Resource>{unicornFur, unicornFur, };

            if (inventory.CanCraft(recipe))

                throw new InvalidOperationException();

        }

        { // we can

            var inventory = new List<Resource>{unicornFur, unicornFur, monsterBone };

            if (!inventory.CanCraft(recipe))

                throw new InvalidOperationException();

        }

        { // we can

            var inventory = new List<Resource>{unicornFur, unicornFur, monsterHide };

            if (!inventory.CanCraft(recipe))

                throw new InvalidOperationException();

        }

        Console.WriteLine("Everything is fine!");

    }

}

​

public static class Extensions

{

    public static bool CanCraft( this IEnumerable<Resource> inventory, IDictionary<Resource, int> uniqueResources, out IEnumerable<Resource> remainingInventory )

    {

        var inv = inventory.ToList();

        remainingInventory = inv;

​

        if (uniqueResources == null || !uniqueResources.Any())

        {

            return true;

        }

​

        // removing all unique resources

        foreach (var item in uniqueResources)

        {

            for (int i = 0; i < item.Value; i++)

            {

                if (!inv.Contains( item.Key ))

                    return false;

                inv.Remove( item.Key );

            }

        }

​

        return true;

    }

​

    public static bool CanCraft( this IEnumerable<Resource> inventory, IDictionary<ResourceKind, int> resources )

    {

        var inv = inventory.ToList();

​

        if (resources == null || !resources.Any())

        {

            return true;

        }

​

        if (!inv.Any())

        {

            return false;

        }

​

        var rk = resources.First().Key;

        var res = resources.ToDictionary( e => e.Key, e => e.Value );

        res[rk] -= 1;

        if (res[rk] == 0)

        {

            res.Remove( rk );

        }

​

​

        foreach (var item in inv.Where( e => (e.Kind & rk) == rk ).ToList())

        {

            inv.Remove( item );

            if (inv.CanCraft( res ))

            {

                return true;

            }

            inv.Add( item );

        }

        return false;

    }

​

    public static bool CanCraft( this IEnumerable<Resource> inventory, Recipe recipe )

    {

        IEnumerable<Resource> remainingInventory;

        return inventory.CanCraft( recipe.UniqueResources, out remainingInventory ) && remainingInventory.CanCraft( recipe.Resources );

    }

}

​

[Flags]

public enum ResourceKind

{

    Bone = 1,

    Hide = 2,

    Organ = 4,

}

​

public class Resource

{

    public int Id

    {

        get;

        set;

    }

​

    public string Name

    {

        get;

        set;

    }

​

    public ResourceKind Kind

    {

        get;

        set;

    }

}

​

public class Recipe

{

    public Dictionary<ResourceKind, int> Resources

    {

        get;

        set;

    }

​

    public Dictionary<Resource, int> UniqueResources

    {

        get;

        set;

    }

}