Gotta Snatch'Em All

MapSet.new()
# => MapSet.new([])

MapSet.new([2, 3, 3, 3, 1, 1, 2, "hello"])
# => MapSet.new([1, 2, 3, "hello"])

MapSet.new([2, 3, 3, 3, 1, 1, 2], fn n -> 10 * n end)
# => MapSet.new([10, 20, 30])

[2, 3, 3, 3, 1, 1, 2] |> MapSet.new() |> MapSet.to_list()
# => [1, 2, 3]

a = MapSet.new([1, 10])
b = MapSet.new([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])

MapSet.size(b)
# => 10

MapSet.member?(a, 10)
# => true

MapSet.subset?(a, b)
# => true

MapSet.disjoint?(a, b)
# => false

a = MapSet.new([1, 10, 100])
b = MapSet.new([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])

MapSet.union(a, b)
# => MapSet.new([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 100])

MapSet.intersection(a, b)
# => MapSet.new([1, 10])

MapSet.difference(a, b)
# => MapSet.new([100])

MapSet.difference(b, a)
# => MapSet.new([2, 3, 4, 5, 6, 7, 8, 9])

MapSet.symmetric_difference(b, a)
# => MapSet.new([2, 3, 4, 5, 6, 7, 8, 9, 100])

a = MapSet.new([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
even = fn n -> rem(n, 2) == 0 end

MapSet.filter(a, even)
# => MapSet.new([2, 4, 6, 8, 10])

MapSet.reject(a, even)
# => MapSet.new([1, 3, 5, 7, 9])

MapSet.split_with(a, even)
# => {MapSet.new([2, 4, 6, 8, 10]), MapSet.new([1, 3, 5, 7, 9])}

Instructions

Your nostalgia for Blorkemon™️ cards is showing no sign of slowing down, you even started collecting them again, and you are getting your friends to join you.

In this exercise, a card collection is represented by a MapSet, since duplicate cards are not important when your goal is to get all existing cards.

1. Start a collection

You really want your friends to join your Blorkemon™️ madness, and the best way is to kickstart their collection by giving them one card.

Implement GottaSnatchEmAll.new_collection, which transforms a card into a collection.

GottaSnatchEmAll.new_collection("Newthree")
# => MapSet.new(["Newthree"])

2. Grow the collection

Once you have a collection, it takes a life of its own and must grow.

Implement GottaSnatchEmAll.add_card, which takes a card and a collection, and returns a tuple with two values: a boolean that indicates if the card was already in the collection, and the collection with the card added.

GottaSnatchEmAll.add_card("Scientuna", MapSet.new(["Newthree"]))
# => {false, MapSet.new(["Newthree", "Scientuna"])}

3. Start trading

Now that your friends are Blorkemon™️ crazy again, you can use this to grow your own collection by trading cards.

Not every trade is worth doing, or can be done at all. You cannot trade a card you don't have, and you shouldn't trade a card for one that you already have.

Implement GottaSnatchEmAll.trade_card, that takes two cards to trade (yours and theirs) and your current collection. The return value is a tuple of two values: a boolean stating if the trade is possible and worth doing, and the collection you would end up with if you did the trade (even if it's not actually possible).

GottaSnatchEmAll.trade_card("Scientuna", "Newthree", MapSet.new(["Scientuna"]))
# => {true, MapSet.new(["Newthree"])}

4. There can be only one of each

You find an old stash of cards in a flea market. You must sort the cards and remove the duplicates to compare the list to your collection.

Implement GottaSnatchEmAll.remove_duplicates which will sort a list of cards and return a list of sorted, unique cards.

GottaSnatchEmAll.remove_duplicates(["Newthree", "Newthree", "Newthree", "Scientuna"])
# => ["Newthree", "Scientuna"]

5. Cards they don't have

Time to feel good about your collection.

Implement GottaSnatchEmAll.extra_cards, which takes your collection and some other collection, and returns the number of cards that the other collection doesn't have.

GottaSnatchEmAll.extra_cards(MapSet.new(["Scientuna"]), MapSet.new(["Newthree", "Scientuna"]))
# => 0

6. Cards they all have

You and your Blorkemon™️ enthusiast friends gather and wonder which cards are the most common.

Implement GottaSnatchEmAll.boring_cards, which takes a list of collections and returns a list of sorted cards that all collections have.

GottaSnatchEmAll.boring_cards([MapSet.new(["Scientuna"]), MapSet.new(["Newthree", "Scientuna"])])
# => ["Scientuna"]

7. All of the cards

Do you and your friends collectively own all of the Blorkemon™️ cards?

Implement GottaSnatchEmAll.total_cards, which takes a list of collections and returns the total number of different cards in the all of the collections.

GottaSnatchEmAll.total_cards([MapSet.new(["Scientuna"]), MapSet.new(["Newthree", "Scientuna"])])
# => 2

8. Shiny for the win

Your nephew is coming to visit you soon, and you feel like impressing him. Kids like shiny things right? Blorkemon™️ cards can be shiny!

Implement GottaSnatchEmAll.split_shiny_cards, which takes a collection and returns a tuple with two lists of sorted cards: one with all the cards that start with "Shiny" and one with the other cards.

GottaSnatchEmAll.split_shiny_cards(MapSet.new(["Newthree", "Scientuna", "Shiny Scientuna"]))
# => {["Shiny Scientuna"], ["Newthree", "Scientuna"]}